Positron emission tomography radiotracers for the complement c3a receptor

Abstract

Compounds and their use for imaging a disease, condition, or disorder associated with one or more Complement system pathways are disclosed.

Description

POSITRON EMISSION TOMOGRAPHY RADIOTRACERS FORTHE COMPLEMENT C3a RECEPTORCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims benefit of U. S. Provisional Application No. 63 / 717,991, filed November 8, 2024, which is incorporated herein by reference in its entirety.FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] This invention was made with government support under grant AG066464 awarded by the National Institutes of Health. The government has certain rights in the invention.BACKGROUND

[0003] The neuroimmune system in the central nervous system (CNS) is important in normal brain development and adult brain function, as well as in response to altered brain homeostasis, tissue injury, or cell death. Dantzer, 2018; Ransohoff et al., 2015. Various degrees of neuroinflammation are associated with different neurological and psychiatric disorders. Nesargikar et al., 2012; Bohlson and Tenner, 2023; Chen et al., 2022; Morgan and Harris, 2015; Wang et al., 2023; Roumenina, 2021; Gedam and Zheng, 2024; Litvinchuk et al.. 2018; Wan et al., 2018; Yao et al., 2013; Nimmo et al., 2024; Mayilyan et al., 2008; Sekar et al., 2016; Mongan et al., 2020; Farsi and Sheng, 2023.

[0004] Remarkably, the same immune factors are involved in normal and pathological processes in the brain. Among those, the Complement system cascade has been attracting much attention. Bohlson and Tenner, 2023. The Complement system is an essential part of the innate immune response and consists of over 30 inactive forms of soluble and membrane-borne proteins, regulators, and receptors that are activated by pathogenic factors. Morgan and Harris, 2015. The Complement system triggers the elimination of pathogens through a sequential enzyme cascade leading to their clearance. Nesargikar et al., 2012. Three major Complement pathways are recognized: the classical pathway, the mannose-binding lectin pathway, and the alternative pathway. Bohlson and Tenner, 2023.

[0005] C3 convertase is an enzyme that activates the Complement cascade by release of C3a, an anaphylatoxin, which is a shared product of the three Complement system pathways and is a selective agonist of C3aR. Bohlson and Tenner, 2023. In human brain, C3aR is mainly expressed by microglia and, to a much lesser extent, by other cells, including oligodendrocyte progenitors, astrocytes, neurons, and endothelial cells. Zhang et al., 2014; brainmaseq.org. C3aR activation on microglia by C3a is one of the principal regulators of immune response in the CNS.

[0006] Dysregulation of C3aR signaling has been implicated in various brain disorders with a neuroinflammatory component. Nesargikar et al., 2012; Bohlson and Tenner, 2023; Chen et al., 2022; Morgan and Harris, 2015; Wang et al., 2023; Roumenina, 2021; Gedam and Zheng, 2024; Litvinchuk et al., 2018; Wan et al., 2018; Yao et al., 2013; Nimmo et al., 2024; Mayilyan et al., 2008; Sekar et al., 2016; Mongan et al., 2020; Farsi and Sheng, 2023.

[0007] In animal models of Alzheimer’s disease (AD) and in postmortem AD specimens, upregulation of C3aR in microglia is located in close proximity to amyloid-beta plaques, which suggests a cascade of events contributing to AD pathology. Gedam and Zheng, 2024. Recent studies demonstrated that inhibition of C3aR reduces AD pathology and ameliorates cognitive deficits in animal models. Litvinchuk et al., 2018; Yao et al., 2023.

[0008] In vascular dementia (VaD), upregulation of C3aR is an important contributor to vascular inflammation. Nimmo et al., 2024. Targeted Complement system therapies, including C3aR antagonists, might benefit patients with VaD by impacting Complement dysregulation. In addition, C3aR antagonists have reduced tissue injury and mortality in murine stroke models. Pekna et al., 2021; Ahmad et al., 2019.

[0009] Several lines of evidence suggest involvement of the Complement system in the pathogenesis of schizophrenia (SCZ). Mayilyan and Weinberger, 2008; Sekar et al., 2016. Increased activity and expression of C3 convertase, among other components of the system, has been reported in SCZ. Sekar et al.. 2016; Mongan et al.. 2020; Farsi et al., 2023. Additionally, a genome-wide association study (GWAS) identified several Complement system components as genetic risk factors upregulated in SCZ. Woo et al., 2020.

[0010] Components of the Complement system are highly sought targets for imaging. Grunenwald et al., 2021. Non-invasive PET imaging of the Complement cascade could advance understanding of the pathways of the innate immune system in CNS disorders and direct development of new therapeutics. Recent research on the Complement system has extended its roles to diversepathologies, further providing rationale for development of the corresponding non-invasive, precision imaging agents. Grunenwald et al., 2021.SUMMARY

[0011] In some aspects, the presently disclosed subject matter provides a compound of formula (I):

[0013] wherein:

[0014] n is an integer selected from 3, 4, and 5;

[0015] Z at each occurrence is independently selected from CR1, CHR1, C=O, N, NR1, N=O, S, and O, wherein a bond between two Z groups bonded to each other may be a single bond or a double bond; wherein a ring structure containing Z comprises a 5-, 6-, or 7-membered heterocyclic or heteroaryl ring containing 1-3 heteroatoms independently selected from O, N and S;

[0016] R1at each occurrence is independently selected from H, substituted or unsubstituted Ci-Cs alkyl, substituted or unsubstituted Ci-Ce alkoxyl, halogen, -SO2N(R6)2, -N(R6)SO2N(R6)2, -SO2R6, -CONHSO2R6, -CONHSO2(NR6)2, substituted or unsubstituted 3- to 10-membered heterocycloalkyl, substituted or unsubstituted C3-C10 cycloalkyl, cyano, substituted or unsubstituted 5- to 10-membered heteroaryl, substituted or unsubstituted C6-Cio aryl, -COR6, -CO2R6, -N(R6)2, -NR6COR6, -CON(R6)2, and -CONCO(R6)2;

[0017] R6at each occurrence is independently selected from H, substituted or unsubstituted Ci-C7 alkyl, substituted or unsubstituted 5- to 10-membered heteroaryl, substituted or unsubstituted Ce-Cio aryl, substituted or unsubstituted C3-C10 cycloalkyl, and substituted or unsubstituted 3- to 10 membered heterocycloalkyl;

[0018] R2, R3, and R4are each independently selected from H, substituted or unsubstituted Ci-Ce alkyl, halogen, substituted or unsubstituted Ci-Ce alkenyl, substituted or unsubstituted C3-C10 cycloalkyl, trifluoromethyl, CO-substituted or unsubstituted C1-C6 alkyl, CO2-substituted or unsubstituted Ci-Ce alkyl, substituted or unsubstituted Ci-C& alkoxyl, and substituted or unsubstituted Ci-Ce alkylthio;

[0019] Y1, Y2, Y3, and Y4are each independently selected from CH, CF, or N, wherein no more than two of Y1, Y2, Y3, and Y4are N, and wherein at least one of Y1, Y2, Y3, Y4is C18F; and

[0020] Y5is selected from CH or N;

[0021] or a pharmaceutically acceptable salt thereof.

[0022] In certain aspects, Y5is CH. In other aspects, Y5is N.

[0023] In certain aspects, one of Y1, Y2, Y3, and Y4is C18F and the remaining three of Y1, Y2, Y3, and Y4are each CH.

[0024] In certain aspects, one R1is a C3-C10 heterocycloalkyl. In particular aspects, the C3-C10 heterocycloalkyl is morpholinyl or aziridinyl. In other aspects, one R1is a 5- to 9-membered heteroaryl. In particular aspects, the 5- to 9-membered heteroaryl is oxadiazolyl or tetrazolyl.

[0025] In certain aspects, R1at each occurrence is independently selected from H, substituted or unsubstituted C1-C8 alkyl, substituted or unsubstituted Ci-G, alkoxyl, halogen, -SO2NH2, -SO2NHCI-C6alkyl, -SO2N(CI-C6alkyl)2, -CONHSO2C1-C6 alkyl, -CONHS O2NH2. -CONHSO2NHC1-C6 alkyl, -CONHSO2N(Ci-Ce alkyl)2. cyano, substituted 5- to 10-membered heteroaryl, -CONH2, -R6NHCO, -COR6, -CO2R6, -N(R6)2, -NHCOR6, -NR6COR6, -CON(R6)2, and -CONCO(R6)2.

[0026] In certain aspects, at least one R1is not H.

[0027] In certain aspects, no more than two of R2, R3, R4and R5are H.

[0028] In certain aspects:

[0033] wherein:

[0034] Y6is selected from CO, N, NR1, CHR1, and CR1;

[0035] Y7and Y8are each independently selected from N, NR1, CHR1, and CR1; and

[0036] Y9is selected from CR1, CHR1, and (CHR1^; or

[0037] (B)

[0039] wherein Y10and Y11are each independently selected from CR1, CHR1, N, and NR1; and Y12is selected from N, NR1, S, and O.

[0040] In particular aspects of (A) at least one of Y7and Y8is CH. In more particular aspects, (A) is:

[0042] In more certain aspects, the compound of formula (I) is compound of formula (I-A):

[0046] In particular aspects, the compound of formula (I-A) is a compound of formula (I-B):

[0048] In more particular aspects, the compound of formula (I-B) is a compound of formula (I- B-i):

[0050] wherein:

[0051] Rlais selected from H, substituted or unsubstituted Ci-Cs alkyl, substituted or unsubstituted Ci-Ce alkoxyl, halogen, -SC>2N(R6)2, -N(R6)SO2N(R6)2, -SO2R6, -C(=O)-NH-SO2R6, -C(=O)-NH-SO2(NR6)2, substituted or unsubstituted 3- to 10-membered heterocycloalkyl, substituted or unsubstituted C3-C10 cycloalkyl, cyano, substituted or unsubstituted 5- to 10-membered heteroaryl, substituted or unsubstituted Ce-Cio aryl, -C(=O)-R6, -CO2-R6, -N(R6)2, -NR6-C(=O)R6, and -C(=O)-N(R6)2;

[0052] R6at each occurrence is independently selected from H, substituted or unsubstituted Ci-Ce alkyl, substituted or unsubstituted 5- to 10-membered heteroaryl, substituted or unsubstituted Ce-Cio aryl, substituted or unsubstituted C3-C10 cycloalkyl, and substituted or unsubstituted 3- to 10-membered heterocycloalkyl;

[0053] R2, R3, and R4are each independently selected from H, substituted or unsubstituted Ci-Ce alkyl, halogen, substituted or unsubstituted Ci-Ce alkenyl, substituted or unsubstituted C3-C10 cycloalkyl, trifluoromethyl, -C(=O)-R7, -C(=O)-O-R7, substituted or unsubstituted Ci-Ce alkoxyl, and substituted or unsubstituted Ci-Ce alkylthio, wherein each R7is independently substituted or unsubstituted Ci-Ce alkyl; provided that at least one of R2, R3, and R4is not H; and

[0054] pharmaceutically acceptable salts thereof.

[0055] In certain aspects, R4is H. In certain aspects. R2and R3are each independently C1-C8 alkyl. In particular aspects, R4is H and R2and R3are each Ci-Cs alkyl.

[0056] In certain aspects, Rlais selected from H and -N(R6)2, wherein R6is H or Ci-Ce substituted or unsubstituted alkyl.

[0057] In certain aspects, Rlais H or -N(R6)2, wherein R6is H or Ci-Ce substituted or unsubstituted alkyl; R2and R3are each independently C1-C8 alkyl; and pharmaceutically acceptable salts thereof.

[0058] In particular aspects, the compound of formula (IB) is selected from:

[0059]

[0060]

[0061]

[0062]

[0063]

[0064]

[0065]

[0066]

[0074] In other aspects, the presently disclosed subject matter provides a compound of formula (I) and a pharmaceutically acceptable carrier.

[0075] In other aspects, the presently disclosed subject matter provides a method for imaging a disease, condition, or disorder associated with one or more Complement system pathways, the method comprising administering a compound of formula (I) or a composition thereof to a subject and taking an image.

[0076] In certain aspects, the compound of formula (I) targets a C3a receptor (C3aR) of the Complement system.

[0077] In particular aspects, the image comprises a positron emission tomography (PET) image.

[0078] In certain aspects, the disease, condition, or disorder comprises an inflammatory disease, disorder, or condition. In particular aspects, the inflammatory disease, disorder, or condition comprises a chronic inflammatory disease, disorder, or condition. In particular aspects, the inflammatory disease, disorder, or condition comprises an inflammation of the central nervous system. In certain aspects, the inflammatory disease, disorder, or condition comprises a neuroinflammatory disease, disorder, or condition.

[0079] In certain aspects, the disease, condition, or disorder comprises a neurological disorder or a psychiatric disorder. In particular aspects, the neurological disorder is selected from Alzheimer's disease (AD), vascular dementia (VD), and stroke. In particular aspects, the psychiatric disorder comprises schizophrenia.

[0080] Certain aspects of the presently disclosed subject matter having been stated hereinabove, which are addressed in whole or in part by the presently disclosed subject matter, other aspects will become evident as the description proceeds when taken in connection with the accompanying Examples and Drawings as best described herein below.BRIEF DESCRIPTION OF THE FIGURES

[0081] The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawings will be provided by the Office upon request and payment of the necessary fee.

[0082] Having thus described the presently disclosed subject matter in general terms, reference will now be made to the accompanying Figures, which are not necessarily drawn to scale, and wherein:

[0083] FIG. 1A and FIG. IB show brain regional time-uptake curves of [18F]2 (FIG. 1A) and [18F]4 (FIG. IB). Data: %ID / g tissue ± SD (n = 3). Abbreviations: CTX - cortex; CB - cerebellum; HIPP - hippocampus; REST - rest of brain.

[0084] FIG. 2 shows a comparison of the whole brain uptake of [18F]2 in control mice (baseline) vs. control mice (self-blocking, 1 mg / kg, i.p.). Blocker 2 was injected i.p. as a suspension in DMSO / saline (1:1). Time-point - 60 min. Data: %ID / g tissue ± SD (n = 5) (ANOVA).

[0085] FIG. 3 shows the dose escalation self-blockade of [18F]2 in LPS-treated mice. Blocker 2 (0.3 mg / kg, 1 mg / kg and 3 mg / kg) was injected i.p. as a suspension in DMSO / saline (1:1). Kill time-point - 15 min post radiotracer injection.

[0086] FIG. 4A and FIG. 4B show a comparison of the whole brain uptake of [18F]2 (FIG. 4A) and [18F]4 (FIG. 4B) in baseline control mice (Ctrl) vs. baseline LPS-treated mice (LPS) vs. blocking LPS-treated mice (LPS block). Kill time-point - 90 min post tracer. The suspension of blocker 2 in Tween-80 / DMSO / saline was injected 60 min prior the radiotracers. The baseline animals were injected with vehicle. Data: %ID / g tissue ± SD (n = 4 - 6).DETAILED DESCRIPTION

[0087] The presently disclosed subject matter now will be described more fully hereinafter with reference to the accompanying Figures, in which some, but not all embodiments of the inventions are shown. Like numbers refer to like elements throughout. The presently disclosed subject matter may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Therefore, it is to be understood that the presently disclosed subject matter is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims.

[0088] In some embodiments, the presently disclosed subject matter provides a compound of formula (I):

[0090] wherein:

[0091] n is an integer selected from 3, 4, and 5;

[0092] Z at each occurrence is independently selected from CR1, CHR1, C=O, N, NR1, N=O, S, and O, wherein a bond between two Z groups bonded to each other may be a single bond or a double bond; wherein a ring structure containing Z comprises a 5-, 6-, or 7-membered heterocyclic or heteroaryl ring containing 1-3 heteroatoms independently selected from O, N and S;

[0093] R1at each occurrence is independently selected from H, substituted or unsubstituted Ci-Cs alkyl, substituted or unsubstituted Ci-Ce alkoxyl, halogen, -SO2N(R6)2, -N(R6)SO2N(R6)2, -SO2R6, -CONHSO2R6, -CONHSO2(NR6)2, substituted or unsubstituted 3- to 10-membered heterocycloalkyl, substituted or unsubstituted C3-Cio cycloalkyl, cyano, substituted or unsubstituted 5- to 10-membered heteroaryl, substituted or unsubstituted C6-Cio aryl, -COR6, -CO2R6, -N(R6)2, -NR6COR6, -CON(R6)2, and -CONCO(R6)2;

[0094] R6at each occurrence is independently selected from H, substituted or unsubstituted Ci-Ce alkyl, substituted or unsubstituted 5- to 10-membered heteroaryl, substituted or unsubstituted Ce-Cio aryl, substituted or unsubstituted C3-C10 cycloalkyl, and substituted or unsubstituted 3- to 10 membered heterocycloalkyl;

[0095] R2, R3, and R4are each independently selected from H, substituted or unsubstituted Ci-Ce alkyl, halogen, substituted or unsubstituted Ci-Ce alkenyl, substituted or unsubstituted C3-C10 cycloalkyl, trifluoromethyl, CO-substituted or unsubstituted Ci-Ce alkyl, CO2-substituted or unsubstituted Ci-Ce alkyl, substituted or unsubstituted Ci-Ce alkoxyl, and substituted or unsubstituted Ci-Ce alkylthio;

[0096] Y1, Y2, Y3, and Y4are each independently selected from CH, CF, or N, wherein no more than two of Y1, Y2, Y3, and Y4are N, and wherein at least one of Y1, Y2, Y3, Y4is C18F; and

[0097] Y5is selected from CH or N;

[0098] or a pharmaceutically acceptable salt thereof.

[0099] In certain embodiments, Y5is CH. In other embodiments, Y5is N.

[0100] In certain embodiments, one of Y1, Y2, Y3, and Y4is C18F and the remaining three of Y1, Y2, Y3, and Y4are each CH.

[0101] In certain embodiments, one R1is a C3-C10 heterocycloalkyl. In particular embodiments, the C3-C10 heterocycloalkyl is morpholinyl or aziridinyl. In other embodiments, one R1is a 5- to 9-membered heteroaryl. In particular embodiments, the 5- to 9-membered heteroaryl is oxadiazolyl or tetrazolyl.

[0102] In certain embodiments, R1at each occurrence is independently selected from H, substituted or unsubstituted Ci-Cs alkyl, substituted or unsubstituted Ci-Ce alkoxyl, halogen, -SO2NH2, -SO2NHCi-C6alkyl. -SO2N(Ci-C6alkyl)2, -CONHSO2CI-C6alkyl, -CONHS O2NH2, -CONHSO2NHCi-Ce alkyl, -CONHSO2N(Ci-Ce alkyl)2, cyano, substituted 5- to 10-membered heteroaryl, -CONH2, -R6NHCO, -COR6, -CO2R6, -N(R6)2, -NHCOR6, -NR6COR6, -CON(R6)2, and -CONCO(R6)2.

[0103] In certain embodiments, at least one R1is not H.

[0104] In certain embodiments, no more than two of R2, R3, R4and R5are H.

[0105] As used herein, Ci-Cg alkyl includes, but is not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, fert-butyl, n-pentyl, sec-pentyl, isopentyl, neopentyl, n-hexyl, sec-hexyl, z?-heptyl, and zt-octyl, as well as positional isomers thereof. As used herein, Ci-Ce alkyl includes, but is not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, secbutyl, tert-butyl, c-pentyl, sec-pentyl, isopentyl, neopentyl, n-hexyl. and sec-hexyl, as well as positional isomers thereof.

[0106] In certain embodiments:

[0117] wherein Y10and Y11are each independently selected from CR1, CHR1, N, and NR1; and Y12is selected from N, NR1, S, and O.

[0118] In particular embodiments of (A) at least one of Y7and Y8is CH. In more particular embodiments, (A) is:

[0120] In more certain embodiments, the compound of formula (I) is compound of formula (I- A):

[0122] wherein Q is selected from:

[0124] In particular embodiments, the compound of formula (I- A) is a compound of formula (I- B):

[0126] In more particular embodiments, the compound of formula (I-B) is a compound of formula (I-B-i):

[0128] wherein:

[0129] Rlais selected from H, substituted or unsubstituted Ci-Cs alkyl, substituted or unsubstituted Ci-C6alkoxyl, halogen, -SO2N(R6)2, -N(R6)SO2N(R6)2, -SO2R6, -C(=O)-NH- SO2R6, -C(=O)-NH-SO2(NR6)2, substituted or unsubstituted 3- to 10-memberedheterocycloalkyl, substituted or unsubstituted C3-C10 cycloalkyl, cyano, substituted or unsubstituted 5- to 10-membered heteroaryl, substituted or unsubstituted Ce-Cio aryl, -C(=O)-R6, -CO2-R6, -N(R6)2, -NR6-C(=O)R6, and -C(=O)-N(R6)2;

[0130] R6at each occurrence is independently selected from H, substituted or unsubstituted Ci-Ce alkyl, substituted or unsubstituted 5- to 10-membered heteroaryl, substituted or unsubstituted Ce-Cio aryl, substituted or unsubstituted C3-C10 cycloalkyl, and substituted or unsubstituted 3- to 10-membered heterocycloalkyl;

[0131] R2, R3, and R4are each independently selected from H, substituted or unsubstituted Ci-Ce alkyl, halogen, substituted or unsubstituted Ci-Ce alkenyl, substituted or unsubstituted C3-C10 cycloalkyl, trifluoromethyl, -C(=O)-R7, -C(=O)-O-R7, substituted or unsubstituted Ci-Ce alkoxyl, and substituted or unsubstituted Ci-Ce alkylthio, wherein each R7is independently substituted or unsubstituted Ci-Ce alkyl; provided that at least one of R2, R3, and R4is not H; and

[0132] pharmaceutically acceptable salts thereof.

[0133] In certain embodiments, R4is H. hi certain embodiments, R2and R3are each independently C1-C8 alkyl. In particular embodiments, R4is H and R2and R3are each Ci-Cx alkyl.

[0134] In certain embodiments, Rlais selected from H and -N(R6)2, wherein R6is H or C1-C6 substituted or unsubstituted alkyl.

[0135] In certain embodiments. Rlais H or -N(R6)2, wherein R6is H or Ci-Ce substituted or unsubstituted alkyl; R2and R3are each independently Ci-Cx alkyl; and pharmaceutically acceptable salts thereof.

[0136] In particular embodiments, the compound of formula (IB) is selected from:

[0150] In more particular embodiments, the compound of formula (I) is selected from:

[0152] In other embodiments, the presently disclosed subject matter provides a compound of formula (I) and a pharmaceutically acceptable carrier.

[0153] In some embodiments, the presently disclosed compounds of formula (I) or formula (IA) bind to the C3a receptor, in certain embodiments, the mammalian C3a receptor. In such embodiments, the presently disclosed compounds of formula (I) or formula (IA) can be used to image a disease, disorder, or condition associated with the C3a receptor. As used herein, the phrase “taking an image” can be used to describe detecting, localizing, and monitoring the disease, disorder, or condition.

[0154] Accordingly, in some embodiments, the presently disclosed subject matter provides a method for imaging a disease, condition, or disorder associated with one or more Complement system pathways, the method comprising administering a compound of formula (I) or formula (la) or a composition thereof to a subject and taking an image.

[0155] In some embodiments, the compound of formula (I) targets a C3a receptor (C3aR) of the Complement system.

[0156] In some embodiments, the image comprises a positron emission tomography (PET) image.

[0157] In some embodiments, the disease, condition, or disorder comprises an inflammatory disease, disorder, or condition. In certain embodiments, the inflammatory disease, disorder, or condition comprises a chronic inflammatory disease, disorder, or condition. In more certain embodiments, the inflammatory disease, disorder, or condition comprises an inflammation of the central nervous system. In particular embodiments, the inflammatory disease, disorder, or condition comprises a neuroinflammatory disease, disorder, or condition.

[0158] In certain embodiments, the disease, condition, or disorder comprises a neurological disorder or a psychiatric disorder. In particular embodiments, the neurological disorder is selected from Alzheimer's disease (AD), vascular dementia (VD), and stroke. In particular embodiments, the psychiatric disorder comprises schizophrenia.

[0159] Additionally, Complement activation has been implicated in the pathogenesis of neurodegenerative disorders in both the central nervous system and the peripheral nervous system including, but not limited to Huntington's disease, Pick's disease, and Gullian Barre syndrome. It is also recognized that Complement activation plays a significant role in allergic lung damage caused by repeated inhalation of antigen, which is consistent with the etiology of asthma. Importantly, it is also recognized that controlling the Complement system can impact the treatment or prevention of disease states, such as sepsis, adult respiratory distress syndrome, nephrites, graft rejection, myocardial ischemia / reperfusion injury, and intestinal ischemia / reperfusion injury.

[0160] Such disease states include, but are not limited to: neurological diseases, such as Alzheimer's disease, multiple sclerosis, Huntington's chorea, Pick's disease, Guillian Barre syndrome, encephalitis, meningitis, stroke, and hemorrhagic stroke; cancer generally and leukemia particularly; allergic and respiratory diseases including allergic dermatitis, anaphylaxis, asthma, eczema, rhinitis, and respiratory distress; cardiovascular or metabolic disease states including shock and hypertension, hyperlipidemia, hypercholesterolemia, edema, and obesity; and inflammatory conditions generally including without limitation, osteoarthritis, ischemia, lung inflammation and rheumatoid arthritis.

[0161] The “subject” treated or imaged by the presently disclosed methods in their many embodiments is desirably a human subject, although it is to be understood that the methods described herein are effective with respect to all vertebrate species, which are intended to be included in the term “subject.” Accordingly, a “subject” can include a human subject for medical purposes, such as for the treatment of an existing condition or disease or the prophylactic treatmentfor preventing the onset of a condition or disease, or an animal subject for medical, veterinary purposes, or developmental purposes. Suitable animal subjects include mammals including, but not limited to, primates, e.g., humans, monkeys, apes, and the like; bovines, e.g.. cattle, oxen, and the like; ovines, e.g., sheep and the like; caprines, e.g., goats and the like; porcines, e.g., pigs, hogs, and the like; equines, e.g., horses, donkeys, zebras, and the like; felines, including wild and domestic cats; canines, including dogs; lagomorphs, including rabbits, hares, and the like; and rodents, including mice, rats, and the like. An animal may be a transgenic animal. In some embodiments, the subject is a human including, but not limited to, fetal, neonatal, infant, juvenile, and adult subjects. Further, a “subject” can include a patient afflicted with or suspected of being afflicted with a condition or disease. Thus, the terms “subject” and “patient” are used interchangeably herein. The term “subject” also refers to an organism, tissue, cell, or collection of cells from a subject.

[0162] In general, a “therapeutically effective amount” of a therapeutic agent refers to the amount of the agent necessary to elicit the desired biological response. As will be appreciated by those of ordinary skill in the art, the effective amount of an agent may vary depending on such factors as the desired biological endpoint, the agent to be delivered, the composition of the pharmaceutical composition, the target tissue or cell, and the like. In some embodiments, the term “therapeutically effective amount” refers to an amount sufficient to reduce or ameliorate the severity, duration, progression, or onset of a disease, disorder, or condition, or one or more symptoms thereof; prevent the advancement of a disease, disorder, or condition, cause the regression of a disease, disorder, or condition; prevent the recurrence, development, onset or progression of a symptom associated with a disease, disorder, or condition, or enhance or improve the prophylactic or therapeutic effect(s) of another therapy.

[0163] The term “combination” is used in its broadest sense and means that a subject is administered at least two agents, more particularly a compound disclosed herein and at least one other therapeutic agent. More particularly, the term “in combination” refers to the concomitant administration of two (or more) active agents for the treatment of a, e.g.. single disease state. As used herein, the active agents may be combined and administered in a single dosage form, may be administered as separate dosage forms at the same time, or may be administered as separate dosage forms that are administered alternately or sequentially on the same or separate days. In one embodiment of the presently disclosed subject matter, the active agents are combined andadministered in a single dosage form. In another embodiment, the active agents are administered in separate dosage forms (e.g., wherein it is desirable to vary the amount of one but not the other). The single dosage form may include additional active agents for the treatment of the disease state.

[0164] Further, the compounds disclosed herein can be administered alone or in combination with adjuvants that enhance stability of the compounds, alone or in combination with one or more therapeutic agents, facilitate administration of pharmaceutical compositions containing them in certain embodiments, provide increased dissolution or dispersion, increase inhibitory activity, provide adjunct therapy, and the like, including other active ingredients. Advantageously, such combination therapies utilize lower dosages of the conventional therapeutics, thus avoiding possible toxicity and adverse side effects incurred when those agents are used as monotherapies.

[0165] The timing of administration of a compound disclosed herein and at least one additional therapeutic agent can be varied so long as the beneficial effects of the combination of these agents are achieved. Accordingly, the phrase “in combination with” refers to the administration of a compound described herein and at least one additional therapeutic agent either simultaneously, sequentially, or a combination thereof. Therefore, a subject administered a combination of a compound described herein and at least one additional therapeutic agent can receive a compound and at least one additional therapeutic agent at the same time (i.e„ simultaneously) or at different times (i.e., sequentially, in either order, on the same day or on different days), so long as the effect of the combination of both agents is achieved in the subject.

[0166] When administered sequentially, the agents can be administered within 1, 5, 10, 30, 60, 120, 180, 240 minutes or longer of one another. In other embodiments, agents administered sequentially, can be administered within 1, 5, 10. 15. 20 or more days of one another. Where the compound described herein and at least one additional therapeutic agent are administered simultaneously, they can be administered to the subject as separate pharmaceutical compositions, each comprising either a compound or at least one additional therapeutic agent, or they can be administered to a subject as a single pharmaceutical composition comprising both agents.

[0167] When administered in combination, the effective concentration of each of the agents to elicit a particular biological response may be less than the effective concentration of each agent when administered alone, thereby allowing a reduction in the dose of one or more of the agents relative to the dose that would be needed if the agent was administered as a single agent. Theeffects of multiple agents may, but need not be, additive or synergistic. The agents may be administered multiple times.

[0168] In some embodiments, when administered in combination, the two or more agents can have a synergistic effect. As used herein, the terms “synergy,” “synergistic,” “synergistically” and derivations thereof, such as in a “synergistic effect” or a “synergistic combination” or a “synergistic composition” refer to circumstances under which the biological activity of a combination of a compound described herein and at least one additional therapeutic agent is greater than the sum of the biological activities of the respective agents when administered individually.

[0169] Synergy can be expressed in terms of a “Synergy Index (SI),” which generally can be determined by the method described by F. C. Kull et al., Applied Microbiology 9, 538 (1961), from the ratio determined by:

[0170] QS / QA + QH / QB = Synergy Index (SI)

[0171] wherein:

[0172] QA is the concentration of a component A, acting alone, which produced an end point in relation to component A;

[0173] Qa is the concentration of component A, in a mixture, which produced an end point;

[0174] QB is the concentration of a component B, acting alone, which produced an end point in relation to component B; and

[0175] Qb is the concentration of component B, in a mixture, which produced an end point.

[0176] Generally, when the sum of QA / QAand QB / QB is greater than one, antagonism is indicated. When the sum is equal to one, additivity is indicated. When the sum is less than one, synergism is demonstrated. The lower the SI, the greater the synergy shown by that particular mixture. Thus, a “synergistic combination” has an activity higher that what can be expected based on the observed activities of the individual components when used alone. Further, a “synergistically effective amount” of a component refers to the amount of the component necessary to elicit a synergistic effect in, for example, another therapeutic agent present in the composition.

[0177] Depending on the specific conditions being treated, the “agent(s)” may be formulated into liquid or solid dosage forms and administered systemically or locally. The agents may be delivered, for example, in a timed- or sustained-slow release form as is known to those skilled in the art. Techniques for formulation and administration may be found in Remington: The Science and Practice of Pharmacy (20th ed.) Lippincott, Williams & Wilkins (2000). Suitable routes mayinclude oral, buccal, by inhalation spray, sublingual, rectal, transdermal, vaginal, transmucosal, nasal or intestinal administration; parenteral delivery, including intramuscular, subcutaneous, intramedullary injections, as well as intrathecal, direct intraventricular, intravenous, intra-articular, intra- sternal, intra-synovial, intra-hepatic, intralesional, intracranial, intraperitoneal, intranasal, or intraocular injections or other modes of delivery.

[0178] For injection, the agents of the disclosure may be formulated and diluted in aqueous solutions, such as in physiologically compatible buffers such as Hank’s solution, Ringer’s solution, or physiological saline buffer. For such transmucosal administration, penetrants appropriate to the barrier to be permeated are used in the formulation. Such penetrants are generally known in the art.

[0179] Use of pharmaceutically acceptable inert carriers to formulate the compounds herein disclosed for the practice of the disclosure into dosages suitable for systemic administration is within the scope of the disclosure. With proper choice of carrier and suitable manufacturing practice, the compositions of the present disclosure, in particular, those formulated as solutions, may be administered parenterally, such as by intravenous injection. The compounds can be formulated readily using pharmaceutically acceptable carriers well known in the art into dosages suitable for oral administration. Such carriers enable the compounds of the disclosure to be formulated as tablets, pills, capsules, liquids, gels, syrups, slurries, suspensions, and the like, for oral ingestion by a subject (e.g., patient) to be treated.

[0180] For nasal or inhalation delivery, the agents of the disclosure also may be formulated by methods known to those of skill in the art, and may include, for example, but not limited to, examples of solubilizing, diluting, or dispersing substances, such as saline; preservatives, such as benzyl alcohol; absorption promoters; and fluorocarbons.

[0181] In particular embodiments, the compound disclosed herein is administered intranasally in a form selected from the group consisting of a nasal spray, a nasal drop, a powder, a granule, a cachet, a tablet, an aerosol, a paste, a cream, a gel, an ointment, a salve, a foam, a paste, a lotion, a cream, an oil suspension, an emulsion, a solution, a patch, and a stick. As used herein, the term administrating via an "intranasal route" refers to administering by way of the nasal structures.

[0182] Pharmaceutical compositions suitable for use in the present disclosure include compositions wherein the active ingredients are contained in an effective amount to achieve its intended purpose. Determination of the effective amounts is well within the capability of thoseskilled in the art, especially in light of the detailed disclosure provided herein. Generally, the compounds according to the disclosure are effective over a wide dosage range. For example, in the treatment of adult humans, dosages from 0.01 to 1000 mg, from 0.5 to 100 mg, from 1 to 50 mg per day, and from 5 to 40 mg per day are examples of dosages that may be used. A non-limiting dosage is 10 to 30 mg per day. The exact dosage will depend upon the route of administration, the form in which the compound is administered, the subject to be treated, the body weight of the subject to be treated, the bioavailability of the compound(s), the adsorption, distribution, metabolism, and excretion (ADME) toxicity of the compound(s), and the preference and experience of the attending physician.

[0183] In addition to the active ingredients, these pharmaceutical compositions may contain suitable pharmaceutically acceptable carriers comprising excipients and auxiliaries which facilitate processing of the active compounds into preparations which can be used pharmaceutically. The preparations formulated for oral administration may be in the form of tablets, dragees, capsules, or solutions.

[0184] Pharmaceutical preparations for oral use can be obtained by combining the active compounds with solid excipients, optionally grinding a resulting mixture, and processing the mixture of granules, after adding suitable auxiliaries, if desired, to obtain tablets or dragee cores. Suitable excipients are, in particular, fillers such as sugars, including lactose, sucrose, mannitol, or sorbitol; cellulose preparations, for example, maize starch, wheat starch, rice starch, potato starch, gelatin, gum tragacanth, methyl cellulose, hydroxypropylmethyl-cellulose, sodium carboxymethyl-cellulose (CMC), and / or polyvinylpyrrolidone (PVP: povidone). If desired, disintegrating agents may be added, such as the cross-linked polyvinylpyrrolidone, agar, or alginic acid or a salt thereof such as sodium alginate.

[0185] Dragee cores are provided with suitable coatings. For this purpose, concentrated sugar solutions may be used, which may optionally contain gum arabic. talc, polyvinylpyrrolidone, carbopol gel, polyethylene glycol (PEG), and / or titanium dioxide, lacquer solutions, and suitable organic solvents or solvent mixtures. Dye-stuffs or pigments may be added to the tablets or dragee coatings for identification or to characterize different combinations of active compound doses.

[0186] Pharmaceutical preparations that can be used orally include push-fit capsules made of gelatin, as well as soft, sealed capsules made of gelatin, and a plasticizer, such as glycerol or sorbitol. The push-fit capsules can contain the active ingredients in admixture with filler such aslactose, binders such as starches, and / or lubricants such as talc or magnesium stearate and, optionally, stabilizers. In soft capsules, the active compounds may be dissolved or suspended in suitable liquids, such as fatty oils, liquid paraffin, or liquid polyethylene glycols (PEGs). In addition, stabilizers may be added.

[0187] Further, one of ordinary skill in the art will recognize that the presently disclosed compounds, and pharmaceutical compositions thereof, include pharmaceutically acceptable salts. Pharmaceutically acceptable salts are generally well known to those of ordinary skill in the art, and include salts of active compounds that can be prepared with relatively nontoxic acids or bases, depending on the particular substituent moieties found on the compounds described herein. The parent form of the compound can differ from the various salt forms in certain physical properties, such as solubility, and the like.

[0188] When compounds of the present disclosure contain relatively acidic functionalities, base addition salts can be obtained by contacting the neutral form of such compounds with a sufficient amount of the desired base, either neat or in a suitable inert solvent or by ion exchange, whereby one basic counterion (base) in an ionic complex is substituted for another. Examples of pharmaceutically acceptable base addition salts include sodium, potassium, calcium, ammonium, organic amino, magnesium, and the like.

[0189] When compounds of the present disclosure contain relatively basic functionalities, acid addition salts can be obtained by contacting the neutral form of such compounds with a sufficient amount of the desired acid, either neat or in a suitable inert solvent or by ion exchange, whereby one acidic counterion (acid) in an ionic complex is substituted for another. Examples of pharmaceutically acceptable acid addition salts include those derived from inorganic acids, organic acids, and amino acids. See, for example, Berge et al, “Pharmaceutical Salts”, Journal of Pharmaceutical Science, 1977, 66, 1-19). Compounds containing both basic and acidic functionalities allow such compounds to be converted into either base or acid addition salts.

[0190] Accordingly, pharmaceutically acceptable salts suitable for use with the presently disclosed subject matter include, by way of example but not limitation, acetate, arginate, benzenesulfonate, benzoate, bicarbonate, bitartrate, bromide, calcium edetate, camsylate, carbonate, monohydrogencarbonate, citrate, edetate, edisylate, estolate, esylate, fumarate, galactonate, gluceptate, gluconate, glutamate, glycollylarsanilate, hexylresorcinate, hydrabamine, hydriodic, hydrobromide, hydrochloride, hydroxynaphthoate, iodide, isethionate, isobutyrate,lactate, lactobionate, malate, maleate, malonate, mandelate, mesylate, methanesulfonate, mucate, napsylate, nitrate, pamoate (embonate), pantothenate, phosphate, phthalate, diphosphate, monohydrogen phosphate, dihydrogen phosphate, polygalacturonate, propionate, salicylate, stearate, subacetate, suberate, succinate, sulfate, monohydrogensulfate, tannate, tartrate, including (+)-tartrates, (-)-tartrates, and mixtures thereof including racemic mixtures, teoclate, p-toluenesulfonate and trifluoroacetate. Other pharmaceutically acceptable salts may be found in, for example, Remington: The Science and Practice of Pharmacy (20th ed.) Lippincott, Williams & Wilkins (2000).

[0191] Unless otherwise noted, the chemical definitions provided immediately herein below are intended to comply with IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Compiled by A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997).

[0192] The term “hydrocarbon” as used herein, refers to any chemical group comprising hydrogen and carbon. A hydrocarbon group may be substituted or unsubstituted. As would be known to one of ordinary skill in the art, all valencies must be satisfied in making any substitutions. The hydrocarbon may be unsaturated, saturated, branched, unbranched, cyclic, polycyclic, or heterocyclic.

[0193] The term “aliphatic” or “aliphatic group”, as used herein, means a straight-chain (i.e., unbranched) or branched, substituted or unsubstituted hydrocarbon chain that is completely saturated or that contains one or more units of unsaturation, or a monocyclic hydrocarbon or bicyclic hydrocarbon that is completely saturated or that contains one or more units of unsaturation, but which is not aromatic (also referred to herein as “carbocyclyl”, “cycloaliphatic”, or “cycloalkyl”), that has a single point of attachment to the rest of the molecule. Unless otherwise specified, aliphatic groups contain 1-6 aliphatic carbon atoms. In some embodiments, aliphatic groups contain 1-5 aliphatic carbon atoms. In some embodiments, aliphatic groups contain 1-4 alipatic carbon atoms. In some embodiments, aliphatic groups contain 1-3 aliphatic carbon atoms. In some embodiments, aliphatic groups contain 1-2 aliphatic carbon atoms. In some embodiments, “cycloaliphatic” (or “carbocyclyl” or “cycloalkyl”) refers to a monocyclic C3-C7 hydrocarbon that is completely saturated or that contains one or more units of unsaturation, but which is not aromatic, that has a single point of attachment to the rest of the molecule. Suitable aliphatic groups include, but are not limited to, linear or branched, substituted or unsubstituted alkyl, alkenyl,alkynyl groups and hybrids thereof such as (cycloalkyl)alkyl, (cycloalkenyl)alkyl, or (cycloalkyl)alkenyl.

[0194] The term “alkane” refers to acyclic branched or unbranched hydrocarbons having the general formula CnH2n+2, and therefore consisting entirely of hydrogen atoms and saturated carbon atoms.

[0195] The term “alkyl” refers to a univalent group derived from an alkane by removal of a hydrogen atom from any carbon atom and having the chemical formula of -CnH2n+1. The groups derived by removal of a hydrogen atom from a terminal carbon atom of unbranched alkanes form a subclass of normal alkyl (n-alkyl) groups H(CH2)n. The groups RCH2, R2CH (R H), and R3C (R H) are primary, secondary and tertiary alkyl groups, respectively.

[0196] An alkyl can be a straightchain (i.e., unbranched) or branched acyclic hydrocarbon having the number of carbon atoms designated (i.e., Ci-10 means one to ten carbons, including 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10 carbons). In particular embodiments, the term “alkyl” refers to C1-20 inclusive, including 1, 2, 3, 4, 5, 6, 7. 8, 9. 10. 11, 12, 13, 14, 15, 16. 17. 18. 19, and 20 carbons. In other embodiments, the alkyl can be a C1-C4 alkyl, including 1, 2, 3, and 4 carbons. In yet other embodiments, the alkyl can be a C1-C6 alkyl, including 1, 2, 3, 4, 5, and 6 carbons. In even yet other embodiments, the alkyl can be a Ci-Cs alkyl, including 1, 2, 3, 4, 5, 6, 7, and 8 carbons.

[0197] “Lower alkyl” refers to an alkyl group having 1 to about 8 carbon atoms (i.e., a Ci-s alkyl), e.g.. 1, 2, 3, 4, 5. 6, 7, or 8 carbon atoms. “Higher alkyl” refers to an alkyl group having about 10 to about 20 carbon atoms, e.g., 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 carbon atoms. In certain embodiments, “alkyl” refers to straight-chain alkyls. In other embodiments, “alkyl” refers to branched alkyls. In certain other embodiments, “alkyl” refers to straight-chain and / or branched alkyls. “Branched” refers to an alkyl group in which a lower alkyl group, such as methyl, ethyl or propyl, is attached to a linear alkyl chain.

[0198] Representative alkyl groups include, but are not limited to. methyl, ethyl, / 7-propyl. isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, rc-pentyl, sec-pentyl, isopentyl, neopentyl, n-hexyl, sec-hexyl, «-heptyl, w-octyl, w-decyl, n-undecyl, and dodecyl.

[0199] Alkyl groups can optionally be substituted (a “substituted alkyl”) with one or more substituents, which can be the same or different. Such substituent groups include, but are not limited to, alkyl, substituted alkyl, cycloalkyl, halogen, acyl, carboxyl, oxo, aryl, substituted aryl, alkoxyl, hydroxyl, nitro, amino, alkylamino, dialkylamino, sulfate, cyano, and mercapto.

[0200] The term “heteroalkyl,” by itself or in combination with another term, means, unless otherwise stated, a stable straight or branched chain having from 1 to 20 carbon atoms or heteroatoms consisting of at least one carbon atom and at least one heteroatom selected from the group consisting of O, N, P, Si and S, and wherein the nitrogen, phosphorus, and sulfur atoms may optionally be oxidized and the nitrogen heteroatom may optionally be quaternized. The heteroatom(s) O. N, P and S and Si may be placed at any interior position of the heteroalkyl group or at the position at which alkyl group is attached to the remainder of the molecule. Examples include, but are not limited to, -CH2-CH2-O-CH3, -CH2-CH2-NH-CH3, -CH2-CH2-N(CH3)-CH3, -CH2-S-CH2-CH3, -CH2-CH2-S(O)-CH3, -CH2-CH2-S(O)2-CH3, -CH=CH-O-CH3, -Si(CH3)3, -CH2-CH=N-OCH3, -CH=CH-N(CH3)- CH3, 0-CH3, -O-CH2-CH3, and -CN. Up to two or three heteroatoms may be consecutive, such as, for example, -CH2-NH-OCH3 and -CH2-O-Si(CH3)3.

[0201] The term “cycloalkane” refers to saturated monocyclic hydrocarbons (with or without side chains), e.g., cyclobutane. Unsaturated monocyclic hydrocarbons having one endocyclic double or one triple bond are called cycloalkenes and cycloalkynes, respectively. Those having more than one such multiple bond are cycloalkadienes, cycloalkatrienes, and the like. The inclusive terms for any cyclic hydrocarbons having any number of such multiple bonds are cyclic olefins or cyclic acetylenes.

[0202] The term “cycloalkyl” refer to a univalent group derived from a cycloalkane by removal of a hydrogen atom from a ring carbon atom. Cycloalkyls can be a mono- or multicyclic ring system of about 3 to about 10 carbon atoms, e.g., 3, 4, 5, 6, 7, 8, 9, or 10 carbon atoms. The cycloalkyl group also can be optionally substituted with a substituent group provided hereinabove for alkyl groups. Representative monocyclic cycloalkyl rings include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and cycloheptyl. Multicyclic cycloalkyl rings include adamantyl, octahydronaphthyl, decalin, camphor, camphane, and noradamantyl, and fused ring systems, such as dihydro- and tetrahydronaphthalene, and the like.

[0203] The term “cycloalkylalkyl” as used herein, refers to a cycloalkyl group, which is attached to the parent molecular moiety through an alkylene moiety, also as defined above, e.g., a C1-20 alkylene moiety. Examples of cycloalkylalkyl groups include cyclopropylmethyl and cyclopentylethyl.

[0204] The terms “cycloheteroalkyl” and “heterocycloalkyl” (or more generally “heterocyclic”) are used interchangeably and refer to an unsaturated ring system, such as a 3- to 10-membersubstituted or unsubstituted cycloalkyl ring system, including one or more heteroatoms, which can be the same or different, and are selected from the group consisting of nitrogen (N), oxygen (O), sulfur (S), phosphorus (P), and silicon (Si), in which the nitrogen, sulfur, and phosphorus heteroatoms may be oxidized and the nitrogen heteroatom may be quatemized. The cyclohetero alkyl ring can be optionally fused to or otherwise attached to other cycloheteroalkyl rings and / or non-aromatic hydrocarbon rings. Representative cycloheteroalkyl ring systems include, but are not limited to pyrrolidinyl, pyrrolinyl, imidazolidinyl, imidazolinyl, pyrazolidinyl, pyrazolinyl, piperidinyl, piperazinyl, indolinyl, quinuclidinyl, morpholinyl, thiomorpholinyl, thiadiazinanyl, tetrahydrofuranyl, and the like.

[0205] The terms “cycloalkylene” and “heterocycloalkylene” refer to the divalent derivatives of cycloalkyl and heterocycloalkyl, respectively.

[0206] As used herein the terms “bicycloalkyl” and “bicycloheteroalkyl” refer to two cycloalkyl or cycloheteroalkyl groups that are bound to one another. Non-limiting examples include bicyclohexane and bipiperidine.

[0207] An “unsaturated hydrocarbon” has one or more double bonds or triple bonds. As used herein, the term “alkene” refers to an acyclic branched or unbranched hydrocarbons having one carbon-carbon double bond and the general formula CnH2n. Acyclic branched or unbranched hydrocarbons having more than one double bond are alkadienes, alkatrienes, and the like.

[0208] More particularly, the term “alkenyl” as used herein refers to a monovalent group derived from a C2-20 inclusive straight or branched hydrocarbon moiety having at least one carbon-carbon double bond by the removal of a single hydrogen molecule. Alkenyl groups include, but are not limited to. ethenyl (i.e., vinyl), 2-propenyl, butenyl, l-methyl-2-buten-l-yl, pentenyl, 2-isopentenyl, hexenyl, octenyl, allenyl, butadienyl, crotyl (but-2-en-l-yl), 2-(butadienyl), 2,4-pentadienyl, 3-(l,4-pentadienyl), and the like, including higher homologs and isomers.

[0209] The term “cycloalkenyl” as used herein refers to a cyclic hydrocarbon containing at least one carbon-carbon double bond. Examples of cycloalkenyl groups include cyclopropenyl, cyclobutenyl, cyclopentenyl, cyclopentadiene, cyclohexenyl, 1,3-cyclohexadiene, cycloheptenyl, cycloheptatrienyl, and cyclooctenyl.

[0210] The term “alkyne” as used herein refers to an acyclic branched or unbranched hydrocarbons having a carbon-carbon triple bond and the general formula CnH2n-2, RC=CR. Acyclic branched orunbranched hydrocarbons having more than one triple bond are known as alkadiynes, alkatriynes, and the like.

[0211] The term “alkynyl” as used herein refers to a monovalent group derived from a straight or branched C2-20 hydrocarbon of a designed number of carbon atoms containing at least one carboncarbon triple bond. Examples of alkynyl groups include, but are not limited to. ethynyl, 2-propynyl (propargyl), 1-propynyl, pentynyl, hexynyl, and heptynyl groups, and the like.

[0212] As used herein, the term “alkylene” refers to an alkanediyl group having the free valencies on adjacent carbon atoms, e.g. -CH(CH3)CH2- propylene (systematically called propane-1, 2-diyl). More particularly, the term “alkylene” by itself or a part of another substituent refers to a straight or branched bivalent aliphatic hydrocarbon group derived from an alkyl group having from 1 to about 20 carbon atoms, e.g., 1, 2, 3, 4. 5, 6, 7. 8, 9, 10, 11, 12, 13, 14, 15. 16. 17. 18. 19. or 20 carbon atoms. The alkylene group can be straight, branched or cyclic. The alkylene group also can be optionally unsaturated and / or substituted with one or more “alkyl group substituents.” There can be optionally inserted along the alkylene group one or more oxygen, sulfur or substituted or unsubstituted nitrogen atoms (also referred to herein as “alkylaminoalkyl”), wherein the nitrogen substituent is alkyl as previously described. Exemplary alkylene groups include methylene (-CH2-); ethylene (-CH2-CH2-); propylene (-(CH2)3-); cyclohexylene (-C6H10-); -CH=CH-CH=CH-; -CH=CH-CH2-; -CH2CH2CH2CH2-, -CH2CH=CHCH2-, -CH2C≡CCH2-, CH2CH2CH(CH2CH2CH3)CH2-, -(CH2)q-N(R)-(CH2)r-, wherein each of q and r is independently an integer from 0 to about 20, e.g., 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20, and R is hydrogen or lower alkyl; methylenedioxyl (-O-CH2-O-); and ethylenedioxyl (-O-(CH2)2-O-). An alkylene group can have about 2 to about 3 carbon atoms and can further have 6-20 carbons. Typically, an alkyl (or alkylene) group will have from 1 to 24 carbon atoms, with those groups having 10 or fewer carbon atoms being some embodiments of the present disclosure. A “lower alkyl” or “lower alkylene” is a shorter chain alkyl or alkylene group, generally having eight or fewer carbon atoms.

[0213] The term “hetero alkylene” by itself or as part of another substituent means a divalent group derived from heteroalkyl, as exemplified, but not limited by, -CH2-CH2-S-CH2-CH2- and -CH2-S-CH2-CH2-NH-CH2-. For heteroalkylene groups, heteroatoms also can occupy either or both of the chain termini (e.g., alkyleneoxo, alkylenedioxo, alkyleneamino, alkylenediamino, and the like). Still further, for alkylene and heteroalkylenelinking groups, no orientation of the linking group is implied by the direction in which the formula of the linking group is written. For example, the formula -C(O)OR’- represents both -C(O)OR’- and -R’OC(O)-.

[0214] The term “arene” refers to a monocyclic and polycyclic aromatic hydrocarbon.

[0215] The term “aryl” refers to a group derived from arenes by removal of a hydrogen atom from a ring carbon atom. Groups similarly derived from heteroarenes are sometimes subsumed in this definition. An aryl group can include, for example, a single ring or multiple rings (such as from 2 to 3 rings), which are fused together or linked covalently.

[0216] The term “heteroaryl” refers to a group formed by removing one or more hydroxy groups from oxoacids that have the general structure RkE(=O)l(OH)m(l ≥ 0), and replacement analogues of such acyl groups. In organic chemistry an unspecified acyl group is commonly a carboxylic acyl group.

[0217] The term “heteroaryl” refers to the class of heterocyclyl groups derived from heteroarenes by removal of a hydrogen atom from any ring atom. A “heteroaryl” group can include from one to four heteroatoms (in each separate ring in the case of multiple rings) selected from N, O, and S, wherein the nitrogen and sulfur atoms are optionally oxidized, and the nitrogen atom(s) are optionally quatemized. A heteroaryl group can be attached to the remainder of the molecule through a carbon or heteroatom. Non-limiting examples of aryl and heteroaryl groups include phenyl, 1 -naphthyl, 2-naphthyl, 4-biphenyl, 1 -pyrrolyl, 2-pyrrolyl, 3-pyrrolyl, 3-pyrazolyl, 2-imidazolyl, 4-imidazolyl, pyrazinyl, 2-oxazolyl, 4-oxazolyl, 2-phenyl-4-oxazolyl, 5-oxazolyl, 3-isoxazolyl, 4-isoxazolyl, 5-isoxazolyl, 2-thiazolyl, 4-thiazolyl, 5- thiazolyl, 2-furyl, 3-furyl, 2-thienyl, 3-thienyl, 2-pyridyl, 3-pyridyl, 4-pyridyl, 2-pyrimidyl, 4- pyrimidyl, 5-benzothiazolyl, purinyl, 2-benzimidazolyl, 5-indolyl, 1 -isoquinolyl, 5- isoquinolyl, 2-quinoxalinyl, 5-quinoxalinyl, 3-quinolyl, and 6-quinolyl. Substituents for each of above noted aryl and heteroaryl ring systems are selected from the group of acceptable substituents described below. The terms “arylene” and “heteroarylene” refer to the divalent forms of aryl and heteroaryl, respectively.

[0218] For brevity, the term “aryl” when used in combination with other terms (e.g., aryloxy, arylthioxy, arylalkyl) includes both aryl and heteroaryl rings as defined above. Thus, the terms “arylalkyl” and “heteroarylalkyl” are meant to include those groups in which an aryl or heteroaryl group is attached to an alkyl group (e.g., benzyl, phenethyl, pyridylmethyl, furylmethyl, and the like) including those alkyl groups in which a carbon atom (e.g., a methylene group) has beenreplaced by, for example, an oxygen atom (e.g., phenoxymethyl, 2-pyridyl oxymethyl, 3-(l-naphthyloxy)propyl, and the like). However, the term “haloaryl,” as used herein is meant to cover only aryls substituted with one or more halogens.

[0219] Where a heteroalkyl, heterocycloalkyl, or heteroaryl includes a specific number of members (e.g. “3 to 7 membered”), the term “member” refers to a carbon or heteroatom.

[0220] Each of above terms defined hereinabove (e.g., “alkyl,” “heteroalkyl,” “cycloalkyl, and “heterocycloalkyl”, “alkenyl”, “alkynyl,” “aryl,” “heteroaryl,” as well as their divalent derivatives) are meant to include both substituted and unsubstituted forms of the indicated group. Optional substituents for each type of group are provided below.

[0221] As used herein, the term “acyl” refers to a group formed by removing one or more hydroxy groups from oxoacids that have the general structure RkE(=O)l(OH)m(l ≥ 0), and replacement analogues of such acyl groups. In organic chemistry an unspecified acyl group is commonly a carboxylic acyl group. For example, in some embodiments, the term acyl includes an organic acid group wherein the -OH of the carboxyl group has been replaced with another substituent and has the general formula RC(=O)-, wherein R is an alkyl, alkenyl, alkynyl, aryl, carbocylic, heterocyclic, or aromatic heterocyclic group as defined herein). As such, the term “acyl” specifically includes arylacyl groups, such as a 2-(furan-2-yl)acetyl)- and a 2-phenylacetyl group. Specific examples of acyl groups include acetyl and benzoyl. Acyl groups also are intended to include amides, -RC(=O)NR’, esters, -RC(=O)OR’, ketones, -RC(=O)R’, and aldehydes, -RC(=O)H.

[0222] The terms “alkoxyl” or “alkoxy” are used interchangeably herein and refer to a saturated (i.e., alkyl-O-) or unsaturated (i.e., alkenyl-O- and alkynyl-O-) group attached to the parent molecular moiety through an oxygen atom, wherein the terms “alkyl,” “alkenyl,” and “alkynyl” are as previously described and can include C1-20 inclusive, linear, branched, or cyclic, saturated or unsaturated oxo-hydrocarbon chains, including, for example, methoxyl, ethoxyl, propoxyl, isopropoxyl, 77-butoxyl, sec-butoxyl, terf-butoxyl, and 77-pentoxyl, neopentoxyl, w-hexoxyl, and the like.

[0223] The term “alkoxyalkyl” as used herein refers to an alkyl-O-alkyl ether, for example, a methoxy ethyl or an ethoxymethyl group.

[0224] “Aryloxyl” refers to an aryl-O- group wherein the aryl group is as previously described, including a substituted aryl. The term “aryloxyl” as used herein can refer to phenyloxyl or hexyloxyl, and alkyl, substituted alkyl, halo, or alkoxyl substituted phenyloxyl or hexyloxyl.

[0225] “Aralkyl” refers to an aryl-alkyl-group wherein aryl and alkyl are as previously described, and included substituted aryl and substituted alkyl. Exemplary aralkyl groups include benzyl, phenylethyl, and naphthylmethyl.

[0226] “Aralkyloxyl” refers to an aralkyl-O- group wherein the aralkyl group is as previously described. An exemplary aralkyloxyl group is benzyloxyl, i.e., C6H5-CH2-O-. An aralkyloxyl group can optionally be substituted.

[0227] “Alkoxycarbonyl” refers to an alkyl-O-C(=O) group. Exemplary alkoxycarbonyl groups include methoxycarbonyl, ethoxycarbonyl, butyloxycarbonyl, and / -butyloxycarbonyl.

[0228] “Aryloxycarbonyl” refers to an aryl-O-C(=O)- group. Exemplary aryloxycarbonyl groups include phenoxy- and naphthoxy-carbonyl.

[0229] “Aralkoxycarbonyl” refers to an aralkyl-O-C(=O)- group. An exemplary aralkoxycarbonyl group is benzyloxycarbonyl.

[0230] The term “acyloxyl” refers to an oxygen-centered radicals consisting of an acyl radical bonded to an oxygen atom, e.g., an acyl-O- group wherein acyl is as previously described.

[0231] The term “amine” refers to a compound formally derived from ammonia by replacing one, two or three hydrogen atoms by hydrocarbyl groups, and having the general structures RNH2 (primary amines), R2NH (secondary amines), R3N (tertiary amines). In some embodiments, the term amino refers to the -NH2 group. More generally, the amino group is -NR'R”, wherein R' and R” are typically selected from hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted heteroalkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted heterocycloalkyl, substituted or unsubstituted aryl, or substituted or unsubstituted heteroaryl.

[0232] The terms “acylamino” and “alkylamino” refer to specific N-substituted organic radicals with acyl and alkyl substituent groups respectively.

[0233] An “aminoalkyl” as used herein refers to an amino group covalently bound to an alkylene linker. More particularly, the terms alkylamino, dialkylamino, and trialkylamino as used herein refer to one, two, or three, respectively, alkyl groups, as previously defined, attached to the parent molecular moiety through a nitrogen atom. The term alkylamino refers to a group having the structure -NHR’ wherein R’ is an alkyl group, as previously defined; whereas the termdialkylamino refers to a group having the structure -NR’R”, wherein R’ and R” are each independently selected from the group consisting of alkyl groups. The term trialkylamino refers to a group having the structure -NR’R”R”’, wherein R’. R”, and R’” are each independently selected from the group consisting of alkyl groups. Additionally, R’, R”, and / or R’” taken together may optionally be -(CH2)k- where k is an integer from 2 to 6. Examples include, but are not limited to, methylamino, dimethylamino, ethylamino. diethylamino, diethylaminocarbonyl, methylethylamino, isopropylamino, piperidine, trimethylamino, and propylamino.

[0234] The terms alkylthioether and thioalkoxyl refer to a saturated (i.e., alkyl-S-) or unsaturated (i.e., alkenyl-S- and alkynyl-S-) group attached to the parent molecular moiety through a sulfur atom. Examples of thioalkoxyl moieties include, but are not limited to, methylthio, ethylthio, propylthio, isopropylthio, zr-butylthio, and the like.

[0235] “Acylamino” refers to an acyl-NH- group wherein acyl is as previously described. “Aroylamino” refers to an aroyl-NH- group wherein aroyl is as previously described.

[0236] The term “carbonyl” refers to a compound containing the carbonyl group, -C(=O)-. The term is commonly used in the restricted sense of aldehydes (R-C(=O)H) and ketones, although it actually includes carboxylic acids and derivatives.

[0237] The term “carboxylic acid” refers to an oxoacids having the structure RC(=O)OH. The term is used as a suffix in systematic name formation to denote the -C(=O)OH group including its carbon atom. In some embodiments, the term “carboxyl” refers to the -COOH group. Such groups also are referred to herein as a “carboxylic acid” moiety.

[0238] “Carbamoyl” refers to an amide group of the formula -C(=O)NH2.

[0239] “Alkylcarbamoyl” refers to a R’RN-C(=O)- group wherein one of R and R’ is hydrogen and the other of R and R’ is alkyl and / or substituted alkyl as previously described.

[0240] “Dialkylcarbamoyl” refers to a R’RN-C(=O)- group wherein each of R and R’ is independently alkyl and / or substituted alkyl as previously described.

[0241] The term carbonyldioxyl, as used herein, refers to a carbonate group of the formula -O-C(=O)-OR.

[0242] The term “cyano” refers to the -C=N group.

[0243] The terms “halo,” “halide,” or “halogen” as used herein refer to fluoro, chloro, bromo, and iodo groups. Additionally, terms such as “haloalkyl,” are meant to include monohaloalkyl andpolyhaloalkyl. For example, the term “halo(Ci-4)alkyl” is mean to include, but not be limited to, trifluoromethyl, 2,2,2-trifluoroethyl, 4-chlorobutyl, 3-bromopropyl, and the like.

[0244] The term “hydroxyl” refers to the -OH group.

[0245] The term “hydroxyalkyl” refers to an alkyl group substituted with an -OH group.

[0246] The term “mercapto” refers to the -SH group.

[0247] The term “oxo compound” refers to a compounds containing an oxygen atom, =0, doubly bonded to carbon or another element. The term thus embraces aldehydes, carboxylic acids, ketones, sulfonic acids, amides and esters. Oxo used as an adjective (and thus separated by a space) modifying another class of compound, as in oxo carboxylic acids, indicates the presence of an oxo substituent at any position. To indicate a double-bonded oxygen that is part of a ketonic structure, the term keto is sometimes used as a prefix, but such use has been abandoned by IUPAC for naming specific compounds. A traditional use of keto is for indicating oxidation of CHOH to C=O in a parent compound that contains OH groups, such as carbohydrates, e.g. 3-ketoglucose. In some embodiments, the term “oxo” as used herein means an oxygen atom that is double bonded to a carbon atom or to another element.

[0248] The term “nitro” refers to the -NO2 group.

[0249] The term “thio” refers to replacement of an oxygen by a sulfur, e.g., PhC(=S)NH2, thiobenzamide.

[0250] The term “thiol” refers to a compounds having the structure RSH (R t H), e.g., MeCH2SH ethanethiol. A thiol also is known by the term “mercaptan.”

[0251] The term “thiohydroxyl” or “thiol,” as used herein, refers to a group of the formula -SH.

[0252] The term “sulfate” refers to the -SO4 group.

[0253] The term “sulfide” refers to a compound having the structure RSR (R t H) and also are referred to as “thioethers.”

[0254] The term “sulfone” refers to a compound having the structure. RS(=O)2R (R t H), e.g., C2HSS(=O)2CH3 ethyl methyl sulfone.

[0255] The term “sulfoxide” refers to a compound having the structure R2S=O (R t H), e.g., Ph2S=O diphenyl sulfoxide.

[0256] The term “ureido” refers to a urea group of the formula -NH — CO — NH2.

[0257] One of ordinary skill in the art would recognize that a structure represented generally by, for example, the formula:

[0259] as used herein refers to a ring structure, for example, but not limited to a 3-carbon, a 4- carbon, a 5 -carbon, a 6-carbon, a 7-carbon, and the like, aliphatic and / or aromatic cyclic compound, including a saturated ring structure, a partially saturated ring structure, and an unsaturated ring structure, comprising a substituent R group, wherein the R group can be present or absent, and when present, one or more R groups can each be substituted on one or more available carbon atoms of the ring structure. The presence or absence of the R group and number of R groups is determined by the value of the variable “n,” which is an integer generally having a value ranging from 0 to the number of carbon atoms on the ring available for substitution. Each R group, if more than one, is substituted on an available carbon of the ring structure rather than on another R group. For example, the structure above where n is 0 to 2 would comprise compound groups including, but not limited to:

[0260]

[0261] and the like.

[0262] A dashed line representing a bond in a cyclic ring structure indicates that the bond can be either present or absent in the ring. That is, a dashed line representing a bond in a cyclic ring structure indicates that the ring structure is selected from the group consisting of a saturated ring structure, a partially saturated ring structure, and an unsaturated ring structure.

[0263] The symbol) denotes the point of attachment of a moiety to the remainder of the molecule.

[0264] When a named atom of an aromatic ring or a heterocyclic aromatic ring is defined as being “absent,” the named atom is replaced by a direct bond.

[0265] Throughout the specification and claims, a given chemical formula or name shall encompass all tautomers, congeners, and optical- and stereoisomers, as well as racemic mixtures where such isomers and mixtures exist.

[0266] Certain compounds of the present disclosure may possess asymmetric carbon atoms (optical or chiral centers) or double bonds; the enantiomers, racemates, diastereomers, tautomers, geometric isomers, stereoisometric forms that may be defined, in terms of absolute stereochemistry, as (R)-or (S)- or, as D- or L- for amino acids, and individual isomers are encompassed within the scope of the present disclosure. The compounds of the present disclosure do not include those which are known in art to be too unstable to synthesize and / or isolate. The present disclosure is meant to include compounds in racemic, scalemic, and optically pure forms. Optically active (R)- and (S)-, or D- and L-isomers may be prepared using chiral synthons or chiral reagents, or resolved using conventional techniques. When the compounds described herein contain olefenic bonds or other centers of geometric asymmetry, and unless specified otherwise, it is intended that the compounds include both E and Z geometric isomers.

[0267] Unless otherwise stated, structures depicted herein are also meant to include all stereochemical forms of the structure; i.e., the R and S configurations for each asymmetric center. Therefore, single stereochemical isomers as well as enantiomeric and diastereomeric mixtures of the present compounds are within the scope of the disclosure.

[0268] As used herein, the term “congener” refers to one of two or more substances related to each other by origin, structure, or function.

[0269] The term “enantiomer” refers to one of a pair of molecular entities which are mirror images of each other and non-superposable.

[0270] The term “stereoisomer” refers to an isomer that possess identical constitution, but which differ in the arrangement of their atoms in space.

[0271] The term “racemate” refers to an equimolar mixture of a pair of enantiomers. It does not exhibit optical activity. The chemical name or formula of a racemate is distinguished from those of the enantiomers by the prefix (±)- or rac- (or racem-) or by the symbols RS and SR.

[0272] The term “diastereoisomerism” refers to stereoisomerism other than enantiomerism. Diastereoisomers (or diastereomers) are stereoisomers not related as mirror images. Diastereoisomers are characterized by differences in physical properties, and by some differences in chemical behavior towards achiral as well as chiral reagents.

[0273] It will be apparent to one skilled in the art that certain compounds of this disclosure may exist in tautomeric forms, all such tautomeric forms of the compounds being within the scope ofthe disclosure. The term “tautomer,” as used herein, refers to one of two or more structural isomers which exist in equilibrium and which are readily converted from one isomeric form to another.

[0274] Unless otherwise stated, structures depicted herein are also meant to include compounds which differ only in the presence of one or more isotopically enriched atoms. For example, compounds having the present structures with the replacement of a hydrogen by a deuterium or tritium, or the replacement of a carbon by13C- or14C-enriched carbon are within the scope of this disclosure.

[0275] The compounds of the present disclosure may also contain unnatural proportions of atomic isotopes at one or more of atoms that constitute such compounds. For example, the compounds may be radiolabeled with radioactive isotopes, such as for example tritium (3H), iodine-125 (125I) or carbon- 14 (14C). All isotopic variations of the compounds of the present disclosure, whether radioactive or not, are encompassed within the scope of the present disclosure.

[0276] The term “about,” when used in connection with one or more numbers or numerical ranges, should be understood to refer to all such numbers, including all numbers in a range and modifies that range by extending the boundaries slightly above and slightly below the numerical values set forth by, for example, in some embodiments, + / -20%, + / - 15%, + / -10%, + / -5%, + / -4%, + / -3%, + / -2%, and + / -1%. The recitation of numerical ranges by endpoints includes all numbers, e.g., whole integers, including fractions thereof, subsumed within that range (for example, the recitation of 1 to 5 includes 1, 2, 3, 4, and 5, as well as fractions thereof, e.g., 1.5, 2.25, 3.75, 4.1, and the like) and any range within that range.

[0277] The phrase “in one embodiment” or “in some embodiments” as used herein does not necessarily refer to the same embodiment, though it may. Furthermore, the phrase “in another embodiment” as used herein does not necessarily refer to a different embodiment, although it may. Thus, as described below, various embodiments of the invention may be readily combined, without departing from the scope or spirit of the invention.

[0278] The terms “comprise(s),” “include(s),” “having,” “has,” “can,” “contain(s),” and variants thereof, as used herein, are intended to be open-ended transitional phrases, terms, or words that do not preclude the possibility of additional acts or structures. The singular forms “a,” “and” and “the” include plural references, i.e., “one or more,” unless the context clearly dictates otherwise. The present disclosure also contemplates other embodiments “comprising,” “consisting of’ and “consisting essentially of,” the embodiments or elements presented herein, whether explicitly setforth or not. Likewise, the term “include” and its grammatical variants are intended to be nonlimiting, such that recitation of items in a list is not to the exclusion of other like items that can be substituted or added to the listed items.EXAMPLES

[0279] The following Examples have been included to provide guidance to one of ordinary skill in the art for practicing representative embodiments of the presently disclosed subject matter. In light of the present disclosure and the general level of skill in the art, those of skill can appreciate that the following Examples are intended to be exemplary only and that numerous changes, modifications, and alterations can be employed without departing from the scope of the presently disclosed subject matter. The synthetic descriptions and specific examples that follow are only intended for the purposes of illustration and are not to be construed as limiting in any manner to make compounds of the disclosure by other methods.EXAMPLE 1

[0280] POSITRON EMISSION TOMOGRAPHY (PET) RADIOTRACERS FOR THE

[0281] COMPLEMENT C3a RECEPTOR (C3aR)

[0282] Overview

[0283] Positron-emission tomography (PET) imaging of the Complement system is a highly sought-after technique that could advance understanding of the innate immune system in central nervous system (CNS) diseases and development of new drugs. PET radiotracers for imaging the Complement system in the CNS, however, are not currently available.

[0284] One aspect of this Example involves the development of a PET radiotracer targeting the C3a receptor (C3aR) of the Complement system. Accordingly, two PET radiotracers, [18F]2 and [18F]4, targeting C3aR and initial in vivo evaluation of the radiotracers in the mouse brain are described herein.

[0285] In this Example, C3aR radiotracers [18F]2 and [18F]4 were synthesized in one step. Both radiotracers demonstrated high brain uptake (6-10 %ID / g tissue) in control mice. The C3aR specificity (18%) of [18F]2 binding in the control brain was determined in a blocking study. The brain uptake of both radiotracers was significantly increased (approximately 2-fold) in a murine model of neuroinflammation, e.g., lipopolysaccharide (LPS)-treated mice. A blocking experiment in LPS-mice showed a dose-dependent reduction in whole brain uptake of [18F]2, demonstratingthat the blocked binding is specific and dependent upon C3aR. The specificity of the C3aR binding increase in murine neuroinflammation versus control brains was 73-77% for radiotracers [18F]2 and [18F]4.

[0286] In sum, [18F]2 and [18F]4 specifically labeled C3aR in murine neuroinflammation and hold promise for further evaluation in relevant model systems.

[0287] Methods

[0288] General

[0289] Analytical thin layer chromatography (TLC) was performed on 0.20-mm silica gel 60 plates POLYGRAM SIL G / UV254 (Machery-Nagel, Germany). The TLC spots were visualized using UV light. Column chromatography for purification of crude products was carried out on silica gel (60, Irregular, particle size 0.040-0.060 mm, VWR). All NMR spectra were recorded with a Bruker AV 500 Ultra instrument. The chemical shifts (8) were expressed in parts per million (ppm).1H-NMRs were referenced to CDCI3 at <57.26 ppm or DMSO-de at 8 2.50 ppm. Signals are reported as multiplet (m), singlet (s), doublet (d). triplet (t), quartet (q), or broad singlet (bs); and coupling constants are reported in Hertz (Hz). Animal protocols were approved by the Animal Care and Use Committee of the Johns Hopkins Medical Institutions.

[0290] Chemistry

[0291] l-(3-Fluoro-3',4'-dimethyl-[l,l'-biphenyl]-4-yl)ethan-l-one (7a) (see International PCT Patent Application Publication No. W02007 / 034282 A2, for Diaryl-imidazole compounds condensed with a heterocycle as C3a receptor antagonists, to Claffey et al., published March 29, 2007): To a solution of l-(4-bromo-2-fluorophenyl)-ethanone (5a) (2 g, 9.21 mmol) and (3,4-dimethylphenyl)boronic acid (6) (2.07 g, 13.82 mmol) in 1,4-dioxane (20.0 mL) was added 6.0 mL of water. The reaction mixture was degassed with argon for about 30 min. After that, Pd(dppf)Ch. DCM (0.37 g, 0.46 mmol) and Na2COa (1.95 g, 18.43 mmol) were added to the reaction mixture and again degassed with argon for another 20 minutes. The reaction mixture was stirred under reflux for 3 h. After cooling down to room temperature, the mixture was extracted with ethyl acetate, washed with brine, dried over Na2SO4. and concentrated under reduced pressure. The crude product was purified by column chromatography (Hexane / EtOAc = 4:6) to afford 7a (1.9 g, 85%) as a white solid. 'H NMR (500 MHz, CDCI3) d 7.96 (t, J = 8.0 Hz, 1H), 7.47 (d. J = 8.2 Hz, 1H), 7.42 (s. 1H), 7.40 - 7.34 (m, 2H), 7.30 - 7.24 (m, 1H), 2.69 (d. J = 4.8 Hz, 3H), 2.37 (s, 3H), 2.35 (s, 3H).

[0292] l-(3',4'-Dimethyl-3-nitro-[l,r-biphenyl]-4-yl)ethan-l-one (7b): To a solution of l-(4-bromo-2-nitrophenyl)ethan-l-one (5b) (2.0 g, 8.19 mmol) and (3,4-dimethylphenyl)boronic acid (6) (1.84 g, 12.30 mmol) in 1,4-dioxane (4.0 mb) was added 20.0 mL of water. The reaction mixture was degassed with argon for about 30 minutes. After that, Pd(dppf)C12. DCM (0.33 g, 0.41 mmol) and NazCCh (1.73 g. 16.39 mmol) were added to the reaction mixture and again degassed with argon for another 20 minutes. The reaction mixture was stirred under reflux for 3 h. After cooling down to room temperature, the mixture was extracted with EtOAc, washed with brine, dried over NaiSC, and concentrated under reduced pressure. The crude product was purified by column chromatography (Hexane / EtOAc = 3:7) to afford 7b (2.0 g, 91%) as a white solid.!H NMR (500 MHz, CDC13) 3 8.26 (d, J= 1.5 Hz, 1H), 7.91 (dd, J= 7.9, 1.6 Hz, 1H), 7.53 (d, J = 7.9 Hz, 1H), 7.42 (s, 1H), 7.40 - 7.36 (m, 1H), 7.28 (s, 1H), 2.60 (s, 3H), 2.38 (s, 3H), 2.36 (s, 3H).

[0293] 2-Bromo-l-(3-fluoro-3',4'-dimethylbiphenyl-4-yl)ethanone (8a) (see International PCT Patent Application Publication No. W02007 / 034282 A2, for Diaryl-imidazole compounds condensed with a heterocycle as C3a receptor antagonists, to Claffey et al., published March 29, 2007): A solution of bromine (0.59 g, 3.73 mmol) in acetic acid (2.0 mL) was added over 1 h to a solution of l-(3-fluoro-3',4'-dimethyl-[l,l'-biphenyl]-4-yl)ethan-l-one (7a) (1.0 g, 3.11 mmol) and acetic acid (10 mL). After 2 h, ethyl acetate (50 mL) was added followed by 10% aqueous Na2S2C>5 (10 mL). A solution of K.2CO3 (20 g) in water (50 mL) was added slowly. The organic layer was separated and washed with brine (100 mL), dried (Na2SC>4) and concentrated under reduced pressure. The crude product was purified by column chromatography (Hexane / EtOAc = 3:7) to afford 8a (0.9 g, 68%) as a white solid.JH NMR (500 MHz. CDCI3) 88.03 (t, J= 8.0 Hz, 1H), 7.47 (d, J= 8.2 Hz, 1H), 7.42 (s, 1H), 7.40 - 7.34 (m, 2H), 7.30 - 7.24 (m, 1H), 4.49 (s, 2H), 2.43 (s, 3H), 2.41 (s, 3H).

[0294] 2-Bromo-l-(3',4'-dimethyl-3-nitro-[l,l'-biphenyl]-4-yl)ethan-l-one (8b): A solution of bromine (0.69 g, 4.45 mmol) in acetic acid (2.0 mL) was added over 1 h to a solution of l-(3',4'-dimethyl-3-nitro-[l,l'-biphenyl]-4-yl)ethan-l-one (7b) (1.0 g, 3.71 mmol) and acetic acid (10 mL). After 2 h, ethyl acetate (50 mL) was added followed by 10% aqueous Na S2O5 (10 mL). A solution of K2CO3 (20 g) in water (50 mL) was added slowly. The organic layer was separated and washed with brine (100 mL), dried (Na2SC>4) and concentrated under reduced pressure. The crude product was purified by column chromatography (Hexane / EtOAc = 3:7) to afford 8b (1 g, 78%)as a white solid. 'H NMR (500 MHz, CDC13) b' 8.38 (s, 1H), 7.96 (d, J= 8.1 Hz, 1H), 7.55 (d, J = 8.2 Hz, 1H), 7.42 (s, 1H), 7.38 (d, 7 = 7.8 Hz, 1H), 7.29 (s, 1H), 4.32 (s, 2H), 2.37 (s, 3H), 2.34 (s, 3H).

[0295] 2-(3-Fluoro-3',4'-dimethylbiphenyl-4-yl)imidazo[l,2-ft]pyridazin-6-amine (2) (see International PCT Patent Application Publication No. W02007 / 034282 A2, for Diaryl-imidazole compounds condensed with a heterocycle as C3a receptor antagonists, to Claffey et al., published March 29, 2007): To a solution of 2-bromo-l-(3-fluoro-3',4'-dimethyl-biphenyl-4-yl)-ethanone (8a) (0.3 g, 0.93 mmol) and ethanol (5 mL) was added pyridazine-3.6-diamine (9b) (0.106 g, 0.97 mmol) and the reaction was then heated to reflux overnight. After cooling to room temperature, the resulting solid was collected by vacuum filtration. The crude product was purified by column chromatography (Hexane / EtOAc = 3:7) to afford 2 (0.12 g, 39%) as a pale brown solid. 'H NMR (500 MHz, DMSO-76) d 8.21 (t, J = 8.3 Hz, 1H), 8.01 (d, J = 4.2 Hz, 1H), 7.77 (d, J = 9.6 Hz, 1H), 7.61-7.56 (m. 3H), 7.50 - 7.46 (m, 1H), 7.24 (d, J= 7.9 Hz. 1H), 6.69 (d, J= 9.6 Hz, 1H), 6.43 (s. 2H), 2.31 (s. 3H). 2.27 (s, 3H).

[0296] 2-(3',4'-Dimethyl-3-nitro-[l,l'-biphenyl]-4-yl)imidazo[l,2-Z>]pyridazin-6-amine (pre-2): To a solution of 2-bromo-l-(3',4'-dimethyl-3-nitro-[l, T-biphenyl]-4-yl)ethan-l-one (8b) (0.3 g, 0.86 mmol) and ethanol (5 mL) was added pyridazine-3,6-diamine (9b) (0.1 g, 0.89 mmol) and the reaction was then heated to reflux overnight. After cooling to room temperature, the resulting solid was collected by vacuum filtration. The crude product was purified by column chromatography (Hexane / EtOAc = 3:7) to afford pre-2 (0.15 g, 88%) as a white solid. 'H NMR (500 MHz, CDCI3) d 7.96 (d, J = 7.9 Hz, 1H), 7.90 (s, 1H), 7.87 (s, 1H), 7.81 (d, J = 8.3 Hz, 1H), 7.72 (d. J= 9.6 Hz, 1H), 7.42 (s, 1H), 7.38 (d. J= 7.7 Hz, 1H), 7.24 (s, 1H), 4.43 (s. 2H), 2.36 (s, 3H), 2.33 (s, 3H).

[0297] 2-(3-Fluoro-3',4'-dimethyl-[l,r-biphenyl]-4-yl)imidazo[l,2- / >]pyridazine (4): To a solution of 2-bromo-l-(3'.4'-dimethyl-biphenyl-4-yl)-ethanone (8a) (0.3 g. 0.93 mmol) and ethanol (15 mL) was added pyridazin-3-amine (0.092 mg, 0.97 mmol) and the reaction was then heated to reflux overnight. After cooling to room temperature, the resulting solid was collected by vacuum filtration. The crude product was purified by column chromatography (Hexane / EtOAc = 3:7) to afford 4 (0.17 g, 55%) as a white solid.JH NMR (500 MHz, CDCI3) 68.48 (d, 7= 4.1 Hz, 1H), 8.37 (t, J = 8.1 Hz, 1H). 8.31 (d,. / = 3.7 Hz, 1H), 7.97 (d, J = 9.1 Hz, 1H), 7.52 (d. J = 8.2Hz, 1H), 7.44 - 7.37 (m, 3H), 7.23 (d, 7= 7.7 Hz, 1H), 7.06 (dd, 7 = 9.1, 4.4 Hz, 1H), 2.35 (s, 3H), 2.32 (s, 3H).

[0298] 2-(3',4'-Dimethyl-3-nitro-[l,l'-biphenyl]-4-yl)imidazo[l,2-Z>]pyridazine (pre-4): To a solution of 2-bromo-l-(3',4'-dimethyl-3-nitro-[l,l'-biphenyl]-4-yl)ethan-l-one (8b) (0.3 g, 0.93 mmol) and ethanol (15 mb) was added pyridazin-3-amine (0.086 g, 0.9 mmol) and the reaction was then heated to reflux overnight. After cooling to room temperature, the resulting solid was collected by vacuum filtration. The crude product was purified by column chromatography (Hexane / EtOAc = 3:7) to afford pre-4 (0.14 g, 42%) as a white solid. 'H NMR (500 MHz, CDCh) 3 8.34 (d, 7= 4.3 Hz, 1H), 8.22 (s, 1H), 8.00 - 7.95 (m, 3H), 7.87 - 7.83 (m, 1H), 7.43 (s, 1H), 7.25 (s, 1H), 7.08 (dd, 7= 9.2, 4.4 Hz, 1H), 2.36 (s, 3H), 2.34 (s, 1H).

[0299] Radiosynthesis of [18F]2 or [18F]4. A solution of [18F] fluoride, Kryptofix 222® (8-12 mg), and potassium oxalate (2 mg) in 1 mL of 50% aqueous acetonitrile was added to the reaction vessel of a GE MicroLab box. The mixture was heated at 120-140 °C under a stream of nitrogen, while water was evaporated azeo tropically under vacuum after the additions of CH3CN (2 x 2 mL). A solution of the corresponding nitro precursor (pre-2 or pre-4) (2 mg) in anhydrous DMSO (0.8 mL) was added to the reaction vessel and heated at 180 °C for 15 min. The reaction mixture was cooled, diluted with 1 mL water, injected onto a reverse-phase semi-preparative HPLC column (see Table 1). The radioactive peak was collected in 50 mL of HPLC water. The solution was transferred through an activated C18 Sep-Pak Light solid-phase extraction (SPE) cartridge (Waters, Milford, MA). After rinsing the SPE with 10 mL water, the product was eluted with ethanol (1 mL) and 0.9% saline (10 mL) into a dose vial with 4 mL saline. The final product [18F]2 or [18F]4 was then analyzed by analytical HPLC using a UV detector at 254 nm (see Table 1) to determine the radiochemical purity and specific radioactivity at the time synthesis ended. The total radiosynthesis time including quality control was 70-75 min.

[0300] Table 1. HPLC conditions for [18F]2 and [18F]4.

[0301] Brain regional biodistribution mouse studies with [I8F]2 and [I8F]4

[0302] Baseline

[0303] Male, CD-I mice weighing 25-30 g from Charles River Laboratories (Wilmington, MA) were used for the studies. The animals (3 per group) were sacrificed by cervical dislocation at 5, 15, 30, 60 and 90 min following injection of the radiotracers (1.8 - 3.7 GBq (50 - 100 pCi), specific radioactivity 129.5 - 288.6 GBq / pmol (3,500 - 7,800 mCi / pmol), in 0.2 mL saline into a lateral tail vein. The brains were rapidly removed and dissected on ice. The brain regions of interest (cortex, hippocampus and cerebellum) were weighed and their radioactivity content was determined using an automated y-counter with a counting error below 3%. The percent of injected dose per gram of tissue (%ID / g tissue) was calculated. All experimental protocols were approved by the Animal Care and Use Committee of the Johns Hopkins Medical Institutions.

[0304] Blocking in control CD-I mice

[0305] A suspension of blocker 2 (1 mg / kg) in 0.1 mL of 50% (v / v) DMSO in saline was given by intraperitoneal injection (i.p.), 5 min before the intravenous (i.v.) injection of [18F]2, whereas baseline mice received the same volume of the vehicle. The animals (4 and 6 mice per group) were euthanized by cervical dislocation at 60 min post tracer injection. The whole brain uptake of [18F]2 at baseline was compared with that of blocking.

[0306] Biodistribution studies in a lipopolysaccharide (LPS) murine model of neuroinflammation.

[0307] These studies were performed similarly to the baseline and blocking experiments in control mice (see hereinabove). A murine model of neuroinflammation was generated by injecting male CD-I mice with LPS (E.coli O11LB4, Calbiochem, San Diego, CA) (10 mg / kg; 0.2 mL; i.p.) as described previously. Qin et al., 2007. The LPS-treated mice with the highest distress score, Hou et al., 2018; Carstens and Moberg, 2000. were selected for the study.

[0308] Dose-escalation blocking in LPS-treated mice

[0309] A suspension of blocker 2 (0.3 mg / kg, 1 mg / kg and 3 mg / kg) in a mixture of DMSO and saline (50:50) was given i.p. (0.1 mL), 15 min before the i.v. injection of [18F]2, whereas baselineLPS mice received vehicle. The animals (3 per group) were euthanized by cervical dislocation at 15 min post tracer injection. The whole brain uptake of [18F]2 was determined as %ID / g tissue.

[0310] Comparison of whole brain uptake of the radiotracers in baseline control mice vs. baseline LPS-treated mice vs. blocking of LPS-treated mice

[0311] The suspension of blocker 2 (1 mg / kg; 0.1 mL) in a mixture of Tween-80, DMSO and saline (2:50:50) was given i.p., 60 min before the i.v. injection of [18F]2 or [18F]4, whereas baseline mice received only vehicle. Animals (4 - 6 mice per group) were euthanized by cervical dislocation at 90 min after radiotracer injection. Whole brain uptake of [18F]2 or [18F]4 in baseline controls and LPS-treated mice was compared (ANOVA) with that of animals who received blocker.

[0312] Results

[0313] Chemistry

[0314] Nitro-precursors pre-2 and pre-4 for18F-labeling were prepared with overall yields of 24-42% (Scheme 2). Standard compound 2 was synthesized as described previously, (International PCT Patent Application Publication No. W02007 / 034282 A2, for Diaryl-imidazole compounds condensed with a heterocycle as C3a receptor antagonists, to Claffey et al., published March 29, 2007), while new compound 4 was synthesized in 3 steps (Scheme 2) with an overall yield of 32%.

[0315] Radiochemistry

[0316] Radiotracers [18F]2 or [18F]4 were prepared using a TRACERlab FX2N radiochemistry module (GE) with non-decay corrected radiochemical yields of 4 ± 0.7% and 6 ± 1.7%, respectively, and with radiochemical purities exceeding 95%. Specific radioactivities at the end-of-synthesis were 155.4 ± 30.7 GBq / pmol (4,200 ± 830 mCi / pmol) and 299.7 ± 81.4 GBq / pmol (8,100 ± 2,200 mCi / pmol), respectively.

[0317] Baseline studies in CD-I control mice

[0318] Both radiotracers [18F]2 or [18F]4 readily entered the control mouse brain (FIG. 1). Among the brain regions studied, the greatest uptake was seen in the cortex and cerebellum and the lowest in the hippocampus. Radiotracer [18F]2 demonstrated high uptake that gradually increased during the course of the 90 min study from 2% ID / g tissue to 9% ID / g tissue. Radiotracer [18F]4 demonstrated reversible brain pharmacokinetics with a peak of 6% ID / g tissue at 30 min postinjection with a gradual decline thereafter.

[0319] Blocking study in CD-I control mice

[0320] The C3aR binding specificity of [18F]2 in normal mouse brain as determined in the blocking experiment (FIG. 2) with administration of 2 suspension (1 mg / kg) was approximately 18%, although statistically it was significant (P = 0.04, ANOVA).

[0321] Dose escalation self-blockade of [1SF]2 in LPS-treated mice

[0322] Brain uptake of [18F]2 in LPS-treated mice was dose-dependently decreased in a selfblockade experiment (FIG. 3). The decrease of uptake was not significant at the dose of blocker 2 of 0.3 mg / kg, but was significant at doses of 1 mg / kg and 3 mg / kg (P = 0.044 and 0.038, correspondingly; ANOVA).

[0323] Biodistribution studies in murine LPS model of neuroinflammation

[0324] At the 90-min time point. [18F]2 demonstrated a 120% increase (2.2-fold) of whole brain uptake (FIG. 4) in the LPS-treated mice (22.3%ID / g tissue) vs. controls (9.9 %ID / g tissue) that was highly significant (P < 0.01, n = 4 - 6, ANOVA). The increase in brain uptake of [18F]2 into the treated brain compared to the control was significantly reduced (77%) by injection of a suspension of 2 (1 mg / kg), 60 min prior to the radiotracer (P = 0.03, n = 4 - 6, ANOVA).

[0325] In a similar experiment with [18F]4, the increase in brain uptake in the LPS-treated mice vs. controls was 81% (P < 0.01, n = 4 - 5, ANOVA). The increase of the brain uptake of [18F]4 in the LPS mice compared to the controls was significantly blocked (73%) by injection of 2 (1 mg / kg) (P < 0.01, n = 4 - 5, ANOVA).

[0326] Discussion

[0327] C3aR is a major part of the Complement system. Bohlson and Tenner, 2023. Previous research has demonstrated that C3aR expression is altered in various conditions and disorders involving neuroinflammation. Nesargikar et al., 2012; Bohlson and Tenner, 2023; Chen et al., 2022; Morgan and Harris, 2015; Wang et al., 2023; Roumenina, 2021; Gedam and Zheng, 2024; Litvinchuk et al., 2018; Wan et al., 2018; Yao et al.. 2013; Nimmo et al., 2024; Mayilyan et al., 2008; Sekar et al., 2016; Mongan et al., 2020; Farsi and Sheng, 2023.

[0328] As of yet, PET imaging of C3aR has not been described. We identified C3aR antagonists 1-3, (International PCT Patent Application Publication No. W02007 / 034282 A2, for Diarylimidazole compounds condensed with a heterocycle as C3a receptor antagonists, to Claffey et al., published March 29. 2007), with in vitro binding affinities in the nanomolar range, low molecularweight, and moderately high lipophilicity that may be suitable for brain PET, Halldin et al., 2001, (Scheme 1).

[0330] Scheme 1. Published C3aR ligands 1-3, (International PCT Patent Application Publication No. W02007 / 034282 A2, for Diaryl-imidazole compounds condensed with a heterocycle as C3a receptor antagonists, to Claffey et al., published March 29, 2007) and new fluoro analog 4 described herein.

[0331] The lead compound structures 1-3 carry methyl groups that potentially can be labeled asnCH3. The radiosynthesis of [nCH3] -labeled 1-3 via C-C-coupling, however, would be complicated. Without wishing to be bound to any one particular theory, it was thought that one of the selected compounds, e.g., compound 2, is directly suitable for labeling with the PET isotope18F via a corresponding nitro precursor. That assumption was based on the fact that the nitro leaving group in the corresponding nitro precursor is activated for nucleophilic fluorination by an electron withdrawing heterocyclic substituent in the ortho position. Smith and March, 2007. Accordingly, the nitro-precursor pre-2 was prepared as shown in Scheme 2.

[0332] Because the fluoro derivative 2 exhibited at least the same binding affinity as that of its des-fluoro analog 1, International PCT Patent Application Publication No. W02007 / 034282 A2, for Diaryl-imidazole compounds condensed with a heterocycle as C3a receptor antagonists, to Claffey et al., published March 29, 2007, (Scheme 1), we expected that the structurally similar fluoro derivative 4 (Scheme 1) would exhibit likewise high binding affinity to its des-fluoro derivative 3. Based on that assumption, the new fluoro compound 4 and corresponding nitroprecursor pre-4 for18F radiolabeling have been synthesized (Scheme 2).

[0333] Scheme 2. Synthesis of fluorinated C3aR compounds 2 and 4 and nitro-precursors pre-2 and pre-4. Reagents and conditions: a) Pd(dppf)Ch. DCM, Na2COs, 1,4-Dioxane / H20, 100 °C, 3h; b) Br2, Acetic acid, rt, 2h; c) Ethanol, reflux, 8h.

[0334] Radiolabeled [18F]2 and [18F]4 (Scheme 3) were prepared with high purity and specific radioactivity by a Kryptofix 222-assisted reaction of the corresponding nitro-precursors pre-2 and pre-4 with [18F]fluoride under the conditions described previously, Horti et al., 1996, followed by HPLC separation and formulation in saline solution with 7% ethanol. The radiolabeling conditions were not optimized in this study, because the radiochemical yields of the final radiotracers were sufficient for animal experiments.

[0335] Scheme 3. Radiosynthesis of [18F]2 and [18F]4.

[0336] Biodistribution studies of [1SF]2 and [18F]4 in control mice

[0337] Previous research demonstrated an elevated expression of Complement receptors in the cerebral cortex and hippocampus. Woo et al., 2020; Nadeau and Rivest, 2001. Initially, to determine if the radiotracers could permeate the blood-brain barrier and enter the brain, regional brain biodistribution studies in control CD-I mice were performed. The studies demonstrated that [18F]2 enters the mouse brain with a gradual increase of uptake from 5 min to 90 min post-injection, with greatest uptake in the cortex and cerebellum (8.5 - 9 %ID / g tissue) and slightly lower uptake in the hippocampus (7 %ID / g tissue) (FIG. 1A). The second radiotracer [18F]4 also demonstrated a high brain uptake with a peak of 6.2%ID / g tissue in the cortex at 30 min after injection, followed by a slow decline. At 90 min post-injection the cortical uptake of [18F]4 was 5%ID / g tissue. Similarto [18F]2, the regional brain uptake of [18F]4 was highest in the cortex and cerebellum, whereas the hippocampus uptake was lower (FIG. IB).

[0338] Comparison of [18F]2 whole brain uptake in control baseline versus control self-blockade showed a modest but significant reduction upon blocking (18%) (FIG. 2). The low specific binding in control animals may be explained in part by a low concentration of C3aR in normal brain. Sun et al., 2024. We studied the brain uptake of [18F]2 and [18F]4 in a murine model of neuroinflammation because PET radiotracers for imaging C3aR may potentially be used in disorders with a neuroinflammatory component. The LPS -induced neuroinflammation model is one of the most common. Qin et al., 2007; Catorce and Gevorkian, 2016. Recent research demonstrated a 300% increase of C3aR protein in the medial prefrontal cortex of wild type mice after systemic treatment with LPS. Sun et al., 2024.

[0339] In the initial experiments, the ratio of whole brain uptake for both tracers [18F]2 and [18F]4 in mice systemically treated with LPS vs. controls was compared (data not shown). Both radiotracers manifested a similar increase (approximately 2 fold) of brain uptake in LPS-treated mice. Previous studies with the classic translocator protein 18 kDa (TSPO) radiotracer [nC]PKl 1195 showed a comparable increase (2.2 fold) of the ipsilateral / contralateral uptake ratio in rats stereotactically injected with LPS in the right striatum, but the ratio was greater for the second-generation TSPO radiotracers [18F]DPA-714 (approximately 2.8 fold), [18F]GE-180 (3.5 fold), Sridharan et al., 2017, and [18F]GE387 (approximately 2.8 fold). Ramakrishnan et al., 2021. The comparable increase of uptake in neuroinflammation of [11C]PK11195 and the presently disclosed C3aR radiotracers ([18F]2 and [18F]4) was encouraging and stimulated further animal experiments.

[0340] The next step in the evaluation of [18F]2 and [18F]4 was assessment of specific binding in LPS-treated animals. To study the saturation of the radiotracer [18F]2 binding in LPS-treated mice, a suspension of 2 was injected under a dose-escalation protocol (FIG. 3). The experiment showed a dose-dependent reduction of the whole brain uptake demonstrating that the blocked binding is specific and dependent upon C3aR. The maximum blocking with a dose of 3 mg / kg was approximately 30% at the 15 min time-point. This initial blocking study had limitations, however, because the solubility of blocker 2 in water is low and the doses of 2 were injected i.p. as a suspension in 50% aqueous DMSO. Compound 4 is even less water-soluble. A literature search did not reveal a blood-brain barrier penetrating and water-soluble C3aR ligand.

[0341] To overcome the issue of low blocker 2 solubility, Tween-80 was used as a solubilizer. The solubility of 2 improved slightly in Tween-80 / water / DMSO (2 / 50 / 50) formulation, and this new suspension formulation was used in further experiments. Additionally, the time between injection of the blocker and radiotracers was increased to one hour so that the blocker suspension could be absorbed more completely. A comparison of the whole brain uptake of [18F]2 (FIG. 4A) and [18F]4 (FIG. 4B) in baseline control mice vs. baseline LPS-treated mice vs. blocking LPS-treated mice was performed. Radiotracer [18F]2 manifested a 2.2-fold increase of uptake in LPS mice versus controls. About 77% of the increased brain uptake in the LPS mice versus controls was blocked with 2 demonstrating that the blocked binding in the LPS mice was specific and dependent on C3aR. Radiotracer [18F]4 manifested a 1.8-fold increase of uptake in LPS mice vs controls. About 73% of increased brain uptake of [18F]4 in the LPS mice versus controls was blocked, also suggesting C3aR binding specificity.

[0342] The limited solubility of the blocker 2 is a hindrance in this study. It is likely that the saturation of binding of [18F]2 and [18F]4 in the blocking experiments was not achieved in full due to an incomplete absorption of the suspension of 2 blocker. The potential solution of this problem would be a comparison of the radiotracer uptake in control and C3aR knockout mice. Such a study could provide a true picture of the specific binding of [18F]2 and [18F]4, not distorted by the poor solubility of the blocker. Another useful pathway is to develop in the future a brain-entering C3aR blocker with better solubility. The development of optimized C3aR radiotracers with less lipophilicity and reduced non-specific binding is also a very interesting future direction.

[0343] Summary

[0344] This Example describes initial PET radiotracers for imaging the Complement C3a receptor (C3aR) in CNS. Radiotracers [18F]2 and [18F]4 were synthesized via nucleophilic radiofluorination of the corresponding nitro-precursors. Both compounds exhibited high brain uptake in control mice (6 - 10 %ID / g tissue) that was significantly increased (1.8-2.2 fold) in an LPS murine model of neuroinflammation that is in agreement with previously established elevated expression of C3aR in LPS-treated mice. Sun et al., 2024. Our experiments with pharmacologic blockade demonstrated a specificity of approximately 18% in control mice. The specificity of the C3aR binding increase in neuroinflammation vs. control brain was 77% ([18F]2) and 73% ([18F]4) as determined by blocking experiments, however, true specificity will be determined using a more soluble blockingagent or other methods. Both radiotracers are promising for further evaluation as potential PET agents for imaging C3aR.REFERENCES

[0345] All publications, patent applications, patents, and other references mentioned in the specification are indicative of the level of those skilled in the art to which the presently disclosed subject matter pertains. All publications, patent applications, patents, and other references are herein incorporated by reference to the same extent as if each individual publication, patent application, patent, and other reference was specifically and individually indicated to be incorporated by reference. It will be understood that, although a number of patent applications, patents, and other references are referred to herein, such reference does not constitute an admission that any of these documents form part of the common general knowledge in the art.

[0346]

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[0356] Litvinchuk A, Wan YW, Swartzlander DB, Chen F, Cole A, Propson NE, et al.Complement C3aR Inactivation Attenuates Tau Pathology and Reverses an Immune Network Deregulated in Tauopathy Models and Alzheimer's Disease. Neuron. 2018;100:1337-53 e5.

[0357] Yao Y, Chang Y, Li S, Zhu J, Wu Y, Jiang X, et al. Complement C3a receptor antagonist alleviates tau pathology and ameliorates cognitive deficits in P301S mice. Brain Res Bull.2023:200:110685.

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[0371] Carstens E, Moberg GP. Recognizing pain and distress in laboratory animals. ILAR J.2000;41:62-71.

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[0374] Horti A, Ravert HT, London ED, Dannals RF. Synthesis of a radiotracer for studying nicotinic acetylcholine receptors: (+ / -)-Exo-2-(2-[F-18]fluoro-5-pyridyl)-7-azabicyclo[2.2.1]heptane. Journal of Labelled Compounds & Radiopharmaceuticals.1996;38:355-65.

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[0376] Sun R, Tang MY, Yang D, Zhang YY, Xu YH, Qiao Y, et al. C3aR in the medial prefrontal cortex modulates the susceptibility to LPS-induced depressive-like behaviors through glutamatergic neuronal excitability. Prog Neurobiol. 2024;236: 102614.

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[0378] Sridharan S, Lepelletier FX, Trigg W, Banister S, Reekie T, Kassiou M, et al.Comparative Evaluation of Three TSPO PET Radiotracers in a LPS-induced Model of Mild Neuroinflammation in Rats. Mol Imaging Biol. 2017;19:77-89.

[0379] Ramakrishnan NK, Hird M, Thompson S, Williamson DJ, Qiao L, Owen DR, et al. Preclinical evaluation of (S)-[(18)F]GE387, a novel 18-kDa translocator protein (TSPO) PET radioligand with low binding sensitivity to human polymorphism rs6971. Eur J Nucl Med Mol Imaging. 2021;49:125-36.

[0380] International PCT Patent Application Publication No. W02007 / 034282 A2, for Diarylimidazole compounds condensed with a heterocycle as C3a receptor antagonists, to Claffey et al., published March 29. 2007.

[0381] Although the foregoing subject matter has been described in some detail by way of illustration and example for purposes of clarity of understanding, it will be understood by those skilled in the art that certain changes and modifications can be practiced within the scope of the appended claims.

Claims

THAT WHICH IS CLAIMED:

1. A compound of formula (I):wherein:n is an integer selected from 3, 4. and 5;Z at each occurrence is independently selected from CR1. CHR1, C=O, N, NR1, N=O, S, and O, wherein a bond between two Z groups bonded to each other may be a single bond or a double bond; wherein a ring structure containing Z comprises a 5-, 6-, or 7-membered heterocyclic or heteroaryl ring containing 1-3 heteroatoms independently selected from O, N and S;R1at each occurrence is independently selected from H, substituted or unsubstituted Ci-Cs alkyl, substituted or unsubstituted Ci-Ce alkoxyl, halogen, -SO2N(R6)2, -N(R6)SO2N(R6)2, -SO2R6, -CONHSO2R6, -CONHSO2(NR6)2, substituted or unsubstituted 3- to 10-membered heterocycloalkyl, substituted or unsubstituted C3-C10 cycloalkyl, cyano, substituted or unsubstituted 5- to 10-membered heteroaryl, substituted or unsubstituted C6-Cio aryl, -COR6, -CO2R6, -N(R6)2, -NR6COR6, -CON(R6)2, and -CONCO(R6)2;R6at each occurrence is independently selected from H, substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted 5- to 10-membered heteroaryl, substituted or unsubstituted C6-C10 aryl, substituted or unsubstituted C3-C10 cycloalkyl, and substituted or unsubstituted 3- to 10 membered heterocycloalkyl;R2, R3, and R4are each independently selected from H, substituted or unsubstituted Ci-Ce alkyl, halogen, substituted or unsubstituted Ci-Ce alkenyl, substituted or unsubstituted C3-C10 cycloalkyl, trifluoromethyl, CO-substituted or unsubstituted C1-C6 alkyl, CO2-substituted or unsubstituted Ci-Ce alkyl, substituted or unsubstituted Ci-Ce alkoxyl, and substituted or unsubstituted Ci-Ce alkylthio;Y1, Y2, Y3, and Y4are each independently selected from CH, CF, or N, wherein no more than two of Y1, Y2, Y3, and Y4are N, and wherein at least one of Y1, Y2, Y3, Y4is C18F; and Y5is selected from CH or N;or a pharmaceutically acceptable salt thereof.

2. The compound of claim 1, wherein Y5is CH.

3. The compound of claim 1, wherein Y5is N.

4. The compound of any one of claims 1 to 3, wherein one of Y1, Y2, Y3, and Y4is C18F and the remaining three of Y1, Y2, Y3, and Y4are each CH.

5. The compound of any one of claims 1 to 4, wherein one R1is a C3-C10 heterocycloalkyl.

6. The compound of claim 5, wherein the C3-C10 heterocycloalkyl is morpholinyl or aziridinyl.

7. The compound of any one of claims 1 to 4, wherein one R1is a 5- to 9-membered heteroaryl.

8. The compound of claim 7, wherein the 5- to 9-membered heteroaryl is oxadiazolyl or tetrazolyl.

9. The compound of claim 1, wherein R1at each occurrence is independently selected from H, substituted or unsubstituted C1-C8 alkyl, substituted or unsubstituted Ci-Ce alkoxyl, halogen, -SO2NH2, -SO2NHC1-C6 alkyl, -SO2N(CI-C6alkyl)2. -CONHSO2CI-C6alkyl, -CONHS O2NH2. -CONHSO2NHC1-C6 alkyl, -CONHSO2N(Ci-Ce alkyl)2. cyano, substituted 5- to 10-membered heteroaryl, -CONH2, -R6NHCO, -COR6, -CO2R6, -N(R6)2, -NHCOR6, -NR6COR6, -CON(R6)2, and -CONCO(R6)2.

10. The compound of claim 9, wherein at least one R1is not H.

11. The compound of claim 1, wherein no more than two of R2, R3, R4and R5are H.

12. The compound of claim 1, wherein:is selected from:(A)wherein:Y6is selected from CO, N, NR1, CHR1, and CR1;Y7and Y8are each independently selected from N, NR1, CHR1, and CR1; andY9is selected from CR1, CHR1, and (CHR1^; or (B)wherein Y10and Y11are each independently selected from CR1, CHR1, N, and NR1; and Y12is selected from N, NR1, S, and O.

13. The compound of claim 12, wherein for (A) at least one of Y7and Y8is CH.

14. The compound of claim 12, wherein (A) is:

15. The compound of claim 1, wherein the compound of formula (I) is compound of formula (I- A):wherein Q is selected from:

16. The compound of claim 15, wherein the compound of formula (I- A) is a compound of formula (I-B):

17. A compound of claim 16, wherein the compound of formula (I-B) is a compound of formula (I-B-i):wherein:Rlais selected from H, substituted or unsubstituted C1-C8 alkyl, substituted or unsubstituted C1-C6 alkoxyl, halogen, -SO2N(R6)2, -N(R6)SO2N(R6)2, -SO2R6, -C(=O)-NH-SO2R6, -C(=O)-NH-SO2(NR6)2, substituted or unsubstituted 3- to 10-membered heterocycloalkyl, substituted or unsubstituted C3-C10 cycloalkyl, cyano, substituted or unsubstituted 5- to 10-membered heteroaryl,substituted or unsubstituted Ce-Cio aryl, -C(=O)-R6, -CO2-R6, -N(R6)2, -NR6-C(=O)R6, and -C(=O)-N(R6)2;R6at each occurrence is independently selected from H, substituted or unsubstituted Ci-Ce alkyl, substituted or unsubstituted 5- to 10-membered heteroaryl, substituted or unsubstituted C6-C10 aryl, substituted or unsubstituted C3-C10 cycloalkyl, and substituted or unsubstituted 3- to 10-membered heterocycloalkyl;R2, R3, and R4are each independently selected from H, substituted or unsubstituted Ci-Ce alkyl, halogen, substituted or unsubstituted Ci-Ce alkenyl, substituted or unsubstituted C3-C10 cycloalkyl, trifluoromethyl, -C(=O)-R7, -C(=O)-O-R7, substituted or unsubstituted Ci-Ce alkoxyl, and substituted or unsubstituted Ci-Ce alkylthio, wherein each R7is independently substituted or unsubstituted Ci-Ce alkyl; provided that at least one of R2, R3, and R4is not H; and pharmaceutically acceptable salts thereof.

18. The compound of claim 17, wherein R4is H.

19. The compound of claim 17 or claim 18, wherein R2and R3are each independently C1-C8 alkyl.

20. The compound of any one of claims 17 to 19, wherein R4is H and R2and R3are each C1-C8 alkyl.

21. The compound of any one of claims 17 to 20, wherein Rlais selected from H and -N(R6)2, wherein R6is H or Ci-Ce substituted or unsubstituted alkyl.

22. The compound of any one of claims 17 to 21, wherein:Rlais H or -N(R6)2, wherein R6is H or Ci-Ce substituted or unsubstituted alkyl;R2and R3are each independently C1-C8 alkyl; andpharmaceutically acceptable salts thereof.

23. The compound of any one of claims 16 to 23, wherein the compound of formula (IB) is selected from:

24. The compound of any one of claims 1 to 23, wherein the compound of formula (I) is selected from:

25. A formulation comprising the compound of any one of claims 1 to 24 and a pharmaceutically acceptable carrier.

26. A method for imaging a disease, condition, or disorder associated with one or more Complement system pathways, the method comprising administering a compound of formula (I) of any one of claims 1 to 24 or a composition of claim 25 to a subject and taking an image.

27. The method of claim 26, wherein the compound of formula (I) targets a C3a receptor (C3aR) of the Complement system.

28. The method of claim 26 or claim 27, wherein the image comprises a positron emission tomography (PET) image.

29. The method of any one of claims 26 to 28, wherein the disease, condition, or disorder comprises an inflammatory disease, disorder, or condition.

30. The method of claim 29, wherein the inflammatory disease, disorder, or condition comprises a chronic inflammatory disease, disorder, or condition.

31. The method of claim 29 or claim 30 wherein the inflammatory disease, disorder, or condition comprises an inflammation of the central nervous system.

32. The method of any one of claims 29 to 31, wherein the inflammatory disease, disorder, or condition comprises a neuroinflammatory disease, disorder, or condition.

33. The method of claim 26, wherein the disease, condition, or disorder comprises a neurological disorder or a psychiatric disorder.

34. The method of claim 33, wherein the neurological disorder is selected from Alzheimer's disease (AD), vascular dementia (VD), and stroke.

35. The method of claim 33, wherein the psychiatric disorder comprises schizophrenia.

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