Process for preparing padeliporfin and intermediates thereof

Abstract

The invention concerns a process for the preparation of a padeliporfin di-potassium salt, the process comprising reacting palladium-bacteriopheophorbide (Pd-Bpheide) with taurine and a base.

Description

[0001] PROCESS FOR PREPARING PADELIPORFIN AND INTERMEDIATES THEREOF

[0002] TECHNICAL FIELD

[0003] The present subject matter relates to a process for preparing drugs and intermediate compounds for photodynamic therapy (PDT). Particularly, the present subject matter relates to a process for preparing bacteriochlorophyll-derived intermediate compounds and drugs.

[0004] REFERENCES

[0005] The following are references considered to be of relevance as a general background art to this disclosure:

[0006] • US 6,333,319

[0007] • US 6,417,195

[0008] • US 6,569,846

[0009] • US 7,947,672

[0010] • EP 1137411

[0011] • EP 1246826

[0012] • WO 2004 / 045492

[0013] • WO 2005 / 120573

[0014] BACKGROUND

[0015] Photodynamic therapy (PDT) represents a novel approach for the treatment of many malignant and non-malignant diseases and has already been approved by several regulatory authorities for the treatment of lung, gastro-intestinal (Gl) and skin cancers.

[0016] The basic principle of PDT is based on light activation of a non-toxic photosensitizer that is administered to the patient prior to illumination. Upon light-activation of the photosensitizer, the photosensitizer reacts with molecular oxygen, which is present in the tissue, to produce cytotoxic reactive oxygen species (ROS). The ROS then induce the death of the cells in the treated tissue.

[0017] In the search for suitable light sensitive molecules or photosensitizers, bacteriochlorophylls (Bchls) appear to have some advantages over porphyrin-based drugs such as Photofrin®, a photosensitizer most commonly used for PDT. Bacteriochlorophylls have a very high extinction coefficient at long wavelengths (Amax=750-780 nm, e=(4-10)xl04M4cm’1), the part of the spectrum where light penetrates deeply into the tissues. Depending on the central metal atom, they also generate ROS at high quantum yield.

[0018] To increase the stability of Bchl derivatives, the central magnesium atom of Bchl derivatives was replaced with other metal atoms, preferably palladium. Palladium increases the oxidation potential of the Bchl macrocycle and at the same time enhances the intersystem crossing (ISC) rate of the molecule to its triplet state, thereby increasing the quantum yield of ROS generation, as described in US 6,333,319.

[0019] Bchl derivatives were found to be very effective in tumor-targeted PDT, wherein the sensitizer preferably accumulates in the tumor cells. US 6,147,195, US 6,333,319, EP 1137411, and EP 1246826 disclose bacteriochlorophyll derivatives particularly useful for tumor-targeted PDT. Palladium bacteriopheophorbide a (Pd-Bpheide), disclosed in EP 1137411, was found to be highly effective against various solid tumors in pre-clinical studies. Pd-Bpheide was also found to be effective against tumors comprising resistant tumor cells.

[0020] Furthermore, Bchl derivatives bearing a net positive or negative charge were found to be highly effective in vascular-targeted PDT (VTP). WO 2004 / 045492 and WO 2005 / 120573 disclose Bchl derivatives which are designed to adhere to and / or accumulate in blood vessels and elicit a VTP effect, whereby new and / or abnormal blood vessels, as found for example in tumors, are affected and damaged upon illumination with the appropriate wavelength. Occlusion of the blood vessels due to VTP arrests tumor growth and eventually leads to tumor necrosis and eradication.

[0021] Mono- and di-anionic derivatives of Pd-Bpheide, such as those disclosed in WO 2004 / 045492, are potential therapeutic VTP agents with high potency and rapid response times (typical IC50 values of 10 pM are observed at 15 minutes incubation time using H5V endothelial cells). The major advantages of the anionic derivatives are (i) improved solubility over Pd-Bpheide, (ii) rapid clearance of the compound from the blood stream, and (iii) very low organ and tissue penetration due to charge repulsion between the negatively charged compound and heparin sulfate which is present in the vasculature. WO 2004 / 045492 discloses the negatively charged sulfonated Pd-Bchl derivative, palladium B^oxo-lS- methoxycarbonylmethyl-rhodobacteriochlorin 131-(2-sulfoethyl) amide di-potassium salt ("padeliporfin"). Padeliporfin was found to be highly effective against various solid tumors in clinical studies due to its anti-vascular activity.

[0022] Methods for the laboratory synthesis of Pd-Bpheide and padeliporfin were disclosed in US 6,569,846 and WO 2004 / 045492, respectively. US 6,569,846 discloses that Pd-Bpheide is prepared from bacteriopheophorbide (Bpheide) by reacting palladium acetate (Pd(OAc)z) and ascorbic acid with Bpheide. The disclosed methods utilize large amounts of starting materials. As disclosed in WO 2004 / 045492, padeliporfin is obtained from Pd-Bpheide by reacting Pd- Bpheide with taurine in the presence of a buffer.

[0023] SUMMARY

[0024] The present disclosure concerns a new process to produce palladium- bacteriopheophorbide a (Pd-Bpheide), a key intermediate in the production of padeliporfin and other photosensitizers used for the treatment of cancer and other conditions. The present disclosure further concerns a new process to produce padeliporfin.

[0025] According to one aspect, the present subject matter provides a process for the preparation of a salt of the compound of Formula (I), e.g., an alkali metal salt comprising one or more monovalent alkali metal cations of the compound of Formula (I), the process comprising the step of reacting palladium-bacteriopheophorbide (Pd-

[0026] Bpheide) of Formula (II) with taurine and a base

[0027]

[0028] According to an embodiment, the base is a non-nucleophilic base comprising a monovalent cation and has a pKa of at least about 10. In some embodiments, the base is selected from a group consisting of sodium hydroxide, sodium carbonate, potassium hydroxide and potassium carbonate. In a specific embodiment, the base is potassium hydroxide. In an embodiment, the process is carried out in the presence of a polar aprotic solvent selected from a group consisting of dimethyl formamide (DMF), N-methyl pyrrolidone (NMP), dimethysulfoxide (DMSO), N,N'-dimethylpropyleneurea (DMPU), Sulfolane, or combinations thereof. In a specific embodiment, the polar aprotic solvent is DMF.

[0029] According to an embodiment, the compound of Formula (I) is isolated from the reaction mixture by including the steps of: (I) adding acetone and water to precipitate the compound of Formula (I) from the mixture; and (ii) filtering the precipitated padeliporfin salt.

[0030] The reaction is carried out at a temperature of between about 40°C and about 60°C.

[0031] According to a further aspect, the present subject matter provides a process for the preparation of palladium-bacteriopheophorbide (Pd-Bpheide) of Formula (II),

[0032] CD the process comprising the step of reacting Bpheide of Formula (III) with ascorbic acid and a palladium reagent in a solvent mixture comprising at least one C1-C4 alcohol and at least one chlorinated organic solvent

[0033] (III).

[0034] According to an embodiment, the palladium reagent is palladium acetate or palladium chloride. In a specific embodiment, the palladium reagent is palladium acetate. In an embodiment, the solvent mixture comprises at least one C1-C4 alcohol selected from a group consisting of methanol, ethanol, n-propanol, isopropanol, butanol, 2-butanol, isobutanol or any combinations thereof; and at least one chlorinated organic solvent selected from a group consisting of chloroform, dichloromethane, tetrachloromethane, 1,1 dichloroethane, 1,2 dichloroethane, 1,1,2 trichloroethane, 1,1,1 trichloroethane, 1,1, 1,2 tetrachloroethane, pentachloroethane, hexachloroethane, 1,2 dichloropropane, chlorobenzene, 1,2 dichlorobenzene and 1,4 dichlorobenzene or any combination thereof. In a specific embodiment, the solvent mixture comprises methanol and chloroform.

[0035] In an embodiment, the volumetric ratio of alcohol to chlorinated organic solvent is between about 1:0.5 and about 1:3. In a specific embodiment, the volumetric ratio of alcohol to chlorinated organic solvent is about 1:1. In another embodiment, the molar ratio of palladium acetate to ascorbic acid is between about 1:5 and about 1:15. In a specific embodiment, the molar ratio of palladium acetate to ascorbic acid is about 1:9. In a further embodiment, the molar ratio of palladium acetate to Bpheide is between about 1:0.1 and about 1:1. In a specific embodiment, the molar ratio of palladium acetate to Bpheide is about 1:0.2. In another embodiment, the ratio of chlorinated organic solvent to Bpheide is between about 75 ml / 1 gram and about 500 ml / 1 gram. In a specific embodiment, the ratio of chlorinated organic solvent to Bpheide is about 167 ml / 1 gram. According to an embodiment, the compound of Formula (II) is isolated from the reaction mixture comprising (i) filtering palladium black from the mixture; (ii) distilling the solvent from the mixture; and (iii) filtering the precipitated Pd-Bpheide.

[0036] The reaction is carried out at a temperature of between about 25°C and about 50°C. In a specific embodiment, the reaction is carried out at a temperature of between about 30°C and about 40°C.

[0037] In an embodiment, the compound of Formula (II) is reacted with taurine and a base to obtain the compound of Formula (I)

[0038] According to a further aspect, the present subject matter provides a process for the preparation of a salt, e.g., an alkali metal salt comprising one or more monovalent alkali metal cations of the compound of Formula (I), the process comprising the following steps: a) reacting Bpheide of Formula (III) with ascorbic acid and a palladium reagent in a solvent mixture comprising at least one C1-C4 alcohol and at least one chlorinated organic solvent to obtain Pd-Bpheide of Formula (II)

[0039] (II); and b) reacting palladium-bacteriopheophorbide (Pd-Bpheide) of Formula (II) with taurine and a base. In an embodiment, the base is a non-nucleophilic base comprising a monovalent cation and has a pKa of at least 10.

[0040] According to an embodiment, the palladium reagent is palladium acetate or palladium chloride. In a specific embodiment, the palladium reagent is palladium acetate. In an embodiment, the solvent mixture comprises at least one C1-C4 alcohol selected from a group consisting of methanol, ethanol, n-propanol, isopropanol, butanol, 2-butanol, isobutanol or any combinations thereof; and at least one chlorinated organic solvent selected from a group consisting of chloroform, dichloromethane, tetrachloromethane, 1,1 dichloroethane, 1,2 dichloroethane, 1,1,2 trichloroethane, 1,1,1 trichloroethane, 1,1, 1,2 tetrachloroethane, pentachloroethane, hexachloroethane, 1,2 dichloropropane, chlorobenzene, 1,2 dichlorobenzene and 1,4 dichlorobenzene or any combination thereof. In a specific embodiment, the solvent mixture comprises methanol and chloroform.

[0041] In an embodiment, the volumetric ratio of alcohol to chlorinated organic solvent is between about 1:0.5 and about 1:3. In a specific embodiment, the volumetric ratio of alcohol to chlorinated organic solvent is about 1:1. In another embodiment, the molar ratio of palladium acetate to ascorbic acid is between about 1:5 and about 1:15. In a specific embodiment, the molar ratio of palladium acetate to ascorbic acid is about 1:9. In a further embodiment, the molar ratio of palladium acetate to Bpheide is between about 1:0.1 and about 1:1. In a specific embodiment, the molar ratio of palladium acetate to Bpheide is about 1:0.2. In another embodiment, the ratio of chlorinated organic solvent to Bpheide is between about 75 ml / 1 gram and about 500 ml / 1 gram. In a specific embodiment, the ratio of chlorinated organic solvent to Bpheide is about 167 ml / 1 gram.

[0042] According to an embodiment, the process includes an intermediate step between step a) and step b) of isolating the compound of Formula (II) from the reaction mixture of step a) comprising (i) filtering palladium black from the mixture; (ii) distilling the solvent from the mixture; and (iii) filtering the precipitated Pd-Bpheide.

[0043] The reaction is carried out at a temperature of between about 25°C and about 50°C. In a specific embodiment, the reaction is carried out at a temperature of between about 30°C and about 40°C.

[0044] According to an embodiment, the base is selected from a group consisting of sodium hydroxide, sodium carbonate, potassium hydroxide and potassium carbonate. In a specific embodiment, the base is potassium hydroxide. In an embodiment, the process is carried out in the presence of a polar aprotic solvent selected from a group consisting of dimethyl formamide (DMF), N-methyl pyrrolidone (NMP), dimethysulfoxide (DMSO), N,N'- dimethylpropyleneurea (DMPU), Sulfolane, or combinations thereof. In a specific embodiment, the polar aprotic solvent is DMF.

[0045] According to an embodiment, the process includes a step after step b) of isolating the compound of Formula (I) from the reaction mixture of step b) comprising: (i) adding acetone and water to precipitate the compound of Formula (I) from the mixture; and (ii) filtering the precipitated padeliporfin salt.

[0046] The reaction is carried out at a temperature of between about 40°C and about 60°C.

[0047] According to an embodiment, the salt comprises one or more cations selected from a group consisting of monovalent alkali metal cations. In an embodiment, the cations are selected from a group consisting of K+, Na+and Li+.

[0048] In an embodiment, the compound of Formula (I) is padeliporfin di-potassium salt.

[0049] DETAILED DESCRIPTION

[0050] Prior to setting forth the present subject matter in detail, it may be helpful to provide definitions of certain terms to be used herein. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as is commonly understood by one of skill in the art to which this subject matter pertains.

[0051] The term "a" or "an" as used herein includes the singular and the plural, unless specifically stated otherwise. Therefore, the terms "a," "an," or "at least one" can be used interchangeably in this application.

[0052] Throughout the application, descriptions of various embodiments use the term "comprising"; however, it will be understood by one of skill in the art, that in some specific instances, an embodiment can alternatively be described using the language "consisting essentially of" or "consisting of".

[0053] For purposes of better understanding the present teachings and in no way limiting the scope of the teachings, unless otherwise indicated, all numbers expressing quantities, percentages, or proportions, and other numerical values used in the specification and claims, are to be understood as being modified in all instances by the term "about." Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and claims are approximations that may vary depending upon the desired properties sought to be obtained. At the very least, each numerical parameter should at least be construed considering the number of reported significant digits and by applying ordinary rounding techniques. In this regard, the term "about" denotes a quantity which may deviate (namely being higher or lower) by up to 10%, 15%, 20%, 25% or even 30%, from the stated quantity. For example, about 10 should be understood to be in the range of 9-11, 8.5-11.5, 8- 12, 7.5-12.5, or even 7-13. Even where a value is given without the "about" qualification, these should be construed to mean to be about the indicated value, namely the value with a possible deviation as noted in this paragraph.

[0054] Process for preparing palladium-bacteriopheophorbide a (Pd-Bpheide)

[0055] The present subject matter provides a process for preparing Pd-Bpheide of Formula (II)

[0056] (ID wherein the process comprises: reacting Bpheide of Formula (III)

[0057] (HD with ascorbic acid and a palladium reagent in a solvent mixture comprising at least one C1-C4 alcohol and at least one chlorinated organic solvent.

[0058] The processes of the present subject matter are advantageous in that they simplify the production of Pd-Bpheide while achieving a higher yield and purity of the product, as compared to the methods known in the prior art. In addition, the processes reduce the amount of hazardous reagents.

[0059] EP 1137411 discloses a process for the synthesis of Pd-Bpheide comprising the insertion of palladium (Pd2+) metal into bacteriopheophorbide a (Bpheide). The source for Pd2+can be any soluble palladium (II) salt, such as for example palladium acetate (Pd(OAc)z). The Pd insertion reaction takes place in the presence of ascorbic acid and comprises the following steps: a) Reduction of Pd2+to Pd° by ascorbic acid; b) Insertion of Pd° into the Bpheide macrocycle; and c) Simultaneous oxidation of the inserted Pd° to Pd2+by dissolved Pd2+which is reduced to Pd°.

[0060] The excess Pd° obtained in steps (a) and (c) that is not inserted into Bpheide, precipitates as palladium black.

[0061] There are some deficiencies related to the known process for synthesis of Pd-Bpheide. Firstly, not all the Bpheide is converted in Pd-Bpheide, resulting in impure Pd-Bpheide, which is contaminated with Bpheide. This phenomenon may be attributed to the fast precipitation of palladium black in the reaction, which removes most of the Pd° before it has time to react. This is caused by the low solubility of Bpheide in chloroform which is used as the reaction solvent. As such, a relatively large volume of chloroform is necessary to dissolve the Bpheide thereby slowing down its reaction with Pd°. As such, a large ratio of chloroform to Bpheide is needed to prepare relatively small amounts of Pd-Bpheide. For example, a ratio of 1.8 liters chloroform per 1 gr Bpheide may be needed to prepare Pd-Bpheide.

[0062] The present inventors discovered that although Bpheide is insoluble in a C1-C4 alcohol such as methanol and only sparingly soluble in a chlorinated organic solvent such as chloroform, the solubility of Bpheide in a chlorinated organic solvent can be substantially increased when a C1-C4 alcohol is added to the chlorinated organic solvent. The significantly increased solubility of Bpheide in the solvent allows for the use of higher concentrations of reactants in the reaction mixture, which results in a drastic reduction of solvents used as well as a more efficient reaction.

[0063] In the above processes for the preparation of compounds of Formula (II), the palladium reagent may be any convenient reactive compound providing palladium in such structures, such as, for instance, palladium acetate and palladium chloride.

[0064] According to an aspect of the present subject matter, Pd-Bpheide is prepared by reacting Bpheide with ascorbic acid and a palladium reagent. In an embodiment, Pd-Bpheide is prepared by adding a first solution comprising palladium acetate and a chlorinated organic solvent to a second solution comprising a C1-C4 alcohol, ascorbic acid, a chlorinated organic solvent and Bpheide. In a specific embodiment, Pd-Bpheide is prepared by adding a first solution comprising the palladium reagent and chloroform, to a second solution comprising methanol, ascorbic acid, chloroform and Bpheide.

[0065] In an embodiment of the present processes, the process for preparing Pd-Bpheide is carried out in a solvent mixture comprising (i) at least one C1-C4 alcohol and (ii) at least one chlorinated organic solvent. The C1-C4 alcohol may be selected from a group consisting of methanol, ethanol, n-propanol, isopropanol, butanol, 2-butanol, isobutanol or any combinations thereof. The chlorinated organic solvent may be selected from a group consisting of chloroform, dichloromethane, tetrachloromethane, 1,1 dichloroethane, 1,2 dichloroethane, 1,1,2 trichloroethane, 1,1,1 trichloroethane, 1,1, 1,2 tetrachloroethane, pentachloroethane, hexachloroethane, 1,2 dichloropropane, chlorobenzene, 1,2 dichlorobenzene and 1,4 dichlorobenzene or any combination thereof. In a specific example, the solvent mixture comprises methanol and chloroform.

[0066] In an embodiment, the volumetric ratio between the C1-C4 alcohol and the chlorinated organic solvent in the solvent mixture is from about 1:0.05 to about 1:2. In another embodiment, the volumetric ratio between the C1-C4 alcohol and the chlorinated organic solvent is from about 1:0.1 to about 1:1.5. In yet another embodiment, the volumetric ratio between the C1-C4 alcohol and the chlorinated organic solvent is from about 1:0.5 to about 1:1.3. In a specific embodiment, the volumetric ratio between the C1-C4 alcohol and the chlorinated organic solvent is about 1:1.

[0067] In an embodiment, the molar ratio between the palladium acetate and the ascorbic acid is from about 1:1 to about 1:25. In another embodiment, the molar ratio between the palladium acetate and the ascorbic acid is from about 1:2 to about 1:20. In yet another embodiment, the molar ratio between the palladium acetate and the ascorbic acid is from about 1:5 to about 1:15. In a specific embodiment, the molar ratio between the palladium acetate and the ascorbic acid is about 1:9.

[0068] In an embodiment, the molar ratio between the palladium acetate and Bpheide is from about 1:0.05 to about 1:2. In another embodiment, the molar ratio between the palladium acetate and Bpheide is from about 1:0.1 to about 1:1. In yet another embodiment, the molar ratio between the palladium acetate and Bpheide is from about 1:0.1 to about 1:0.5. In a specific embodiment, the molar ratio between the palladium acetate and Bpheide is about 1:0.2.

[0069] In an embodiment, the ratio between the chlorinated organic solvent and Bpheide is from about 50 ml of solvent per gram of Bpheide to about 1000 ml of solvent per gram of Bpheide. In another embodiment the ratio between the chlorinated organic solvent and Bpheide is from about 75 ml of solvent per gram of Bpheide to about 500 ml of solvent per gram of Bpheide. In yet another embodiment, the ratio between the chlorinated organic solvent and Bpheide is from about 100 ml of solvent per gram of Bpheide to about 300 ml of solvent per gram of Bpheide. In a specific embodiment, the ratio between the chlorinated organic solvent and Bpheide is about 167 ml of solvent per gram of Bpheide.

[0070] In one embodiment, the process to prepare Pd-Bpheide is carried out at a temperature from about 20°C to about 75°C, preferably from about 25°C to about 50°C, more preferably from about 30°C to about 40°C. In a preferred embodiment, the process to prepare Pd- Bpheide is carried out at a temperature of about 35°C.

[0071] According to an embodiment, the compound of Formula (II) may be isolated from the reaction mixture. The step of isolating may comprise at least one of: a) filtering palladium black from the mixture; b) distilling the solvent from the mixture; and c) filtering the precipitated Pd-Bpheide.

[0072] According to an embodiment, the Pd-Bpheide is present at a purity of at least 80%, at least 85%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%.

[0073] Process for preparing padeliporfin

[0074] In another embodiment, the present subject matter provides a process for preparing a salt of the compound of Formula (I) wherein the process comprises: reacting palladium-bacteriopheophorbide (Pd-Bpheide) of Formula (II)

[0075]

[0076] CD with taurine and a base.

[0077] The processes of the present subject matter are advantageous in that they simplify the production of padeliporfin while achieving a higher yield and purity of the product, as compared to the methods known in the prior art. In addition, the processes reduce the amount of hazardous reagents.

[0078] US 7,947,672 discloses preparing padeliporfin di-potassium from Pd-Bpheide by reacting Pd-Bpheide with taurine (H2NCH2CH2SO3H), in a buffer and a DMSO / H2O solvent, followed by precipitation and purification of the padeliporfin. The process for preparing padeliporfin as described in US 7,947,672 uses DMSO as a solvent, as well as a basic phosphate buffer to maintain the correct pH.

[0079] According to an embodiment, the compound of Formula (I) is in the form of a salt. The salt comprises one or more cations selected from a group consisting of monovalent alkali metal cations. The cations may be cations selected from a group consisting of K+, Na+and Li+. In a specific embodiment, the compound of Formula (I) is padeliporfin di-potassium salt.

[0080] According to an aspect of the present subject matter, padeliporfin is prepared by reacting Pd-Bpheide with taurine and a base. In another embodiment, padeliporfin is prepared by reacting Pd-Bpheide with taurine and a base in the presence of a polar aprotic solvent. In a specific embodiment, padeliporfin is prepared by reacting Pd-Bpheide with taurine and potassium hydroxide in the presence of dimethyl formamide as a solvent. In an embodiment of the present processes, the base used for preparing padeliporfin is a non-nucleophilic base which comprises a monovalent cation. The base has a pKa of at least about 8, preferably of at least about 9 and more preferably of at least about 10. Suitable non- nucleophilic bases are those that are capable of deprotonating taurine zwitterion. The base may be selected from a group consisting of sodium hydroxide, sodium carbonate, potassium hydroxide and potassium carbonate. In a specific embodiment, the base is potassium hydroxide.

[0081] The process for preparing padeliporfin may be carried out in the presence of a polar aprotic solvent. According to the present subject matter, the polar aprotic solvent may be selected from a group consisting of dimethyl formamide (DMF), N-methyl pyrrolidone (NMP), dimethysulfoxide (DMSO), N,N'-dimethylpropyleneurea (DMPU), Sulfolane, or combinations thereof. In a specific embodiment, the solvent is DMF.

[0082] In one embodiment, the process to prepare padeliporfin is carried out at a temperature from about 20°C to about 80°C, preferably from about 30°C to about 70°C, more preferably from about 40°C to about 60°C. In a preferred embodiment, the process to prepare padeliporfin is carried out at a temperature of about 50°C.

[0083] According to an embodiment, the compound of Formula (I) may be isolated from the reaction mixture. The step of isolating may comprise at least one of: a) adding acetone and water to precipitate the compound of Formula (I) from the mixture; and b) filtering the precipitated padeliporfin salt.

[0084] According to an embodiment, the padeliporfin is present at a purity of at least 80%, at least 85%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%.

[0085] In yet another embodiment, Pd-Bpheide and / or padeliporfin can be optionally purified by any additional conventional techniques well-known in the art. Such purification techniques can be selected, without limitation, from a group consisting of precipitation, crystallization, extraction, slurring, washing in a suitable solvent, filtration, dissolution in a suitable solvent, re- precipitation by addition of a second solvent in which the compound is insoluble, and a combination thereof.

[0086] The abovementioned reactions may be monitored using any suitable method, which can include, for example, chromatographic methods such as, e.g., high performance liquid chromatography (HPLC), thin layer chromatography (TLC), and the like. In another embodiment, the present subject matter provides a process for preparing a salt of the compound of Formula (I) wherein the process comprises: a) reacting Bpheide of Formula III with ascorbic acid and palladium acetate in a solvent mixture comprising at least one Cl-

[0087] C4 alcohol and at least one chlorinated organic solvent to obtain palladium- bacteriopheophorbide (Pd-Bpheide) of Formula (II).

[0088] b) reacting Pd-Bpheide of Formula (II) with taurine and a base.

[0089] The following examples illustrate the practice of the present subject matter in some of its embodiments. However, they should not be construed as limiting the scope of the present subject matter. Other embodiments will be apparent to one skilled in the art from consideration of the specification and examples. It is intended that the specification, including the examples, is considered exemplary only without limiting the scope and spirit of the present subject matter.

[0090] EXAMPLE 1 - Preparation of Pd-Bpheide

[0091] An exemplary experimental procedure for producing Pd-Bpheide is described as follows:

[0092] A 20-1 iter reactor was charged with 7.8 Kg methanol which was then heated to 35°C. The reactor was then charged with 780 gr (4.43 mol) of ascorbic acid. The contents of the reactor were then stirred under N? until all the ascorbic acid dissolved. 13.1 Kg chloroform and 60 gr (98.36 mmol) of Bpheide were then added to the reactor. The contents were continually stirred at 35°C under N?. A palladium acetate (Pd(OAc)z) solution in chloroform was prepared in a separate vessel by adding 1.8 Kg chloroform and 110.5 gr (0.491 mol) Pd(OAc)z to the vessel. The contents were stirred until all the palladium acetate dissolved.

[0093] The palladium acetate solution was added to the 20-liter reactor over a period of 10-15 minutes while constantly stirring. The solution was stirred for a further 15 minutes at 35°C under N2. While stirring, 300 ml of water was added into the reaction mixture. The solution was cooled to 15-20°C.

[0094] The palladium black precipitate formed in the reaction mixture was filtered out. The filtrate was transferred to a stirred tank containing 29.7 Kg of water and 4.5 Kg of chloroform. The 20-1 iter reactor was washed with 4.5 Kg chloroform. The chloroform used for washing was filtered through the same filter used for filtration of the palladium black. The filtered chloroform was combined with the previous filtrate. The mixture of filtrates was stirred for 10-15 minutes. After 20-30 minutes, the phases of the mixture separated. The layers were separated, and the chloroform (bottom layer) solution was transferred into a reactor. The chloroform solution was vacuum distilled to a final volume of 8.1-8.5 liter. After reaching the desired volume, the solution was heated to 60°C, at atmospheric pressure for 5-15 minutes. The solution was then cooled to 10°C over a period of 3-3.5 hours until a slurry was obtained. The slurry was stirred for 30-40 minutes at 10°C and then filtered over a 0.45p Teflon membrane. The filtered product was washed with 250 ml of cold (4°C) chloroform. The product was dried under vacuum oven at 40°C while maintaining an N2 atmosphere for a minimum of 12 hours. The dried product was ground to obtain the required particle size. The ground product was dried for an additional 24 hours at 40°C while maintaining an N2 atmosphere.

[0095] Over a series of batches, a conversion rate of 100% was achieved and the weight of Pd- Bpheide was 52-60 grams with a purity greater than 96%.

[0096] EXAMPLE 2 - Preparation of Pd-Bpheide

[0097] An exemplary experimental procedure for producing Pd-Bpheide is described as follows:

[0098] A 50 L reactor was charged with 17.2 Kg methanol which was then heated to 35°C. The reactor was then charged with 1716 grams (9.75mol) of ascorbic acid and stirred under N2 at a minimum temperature of 34°C until all the ascorbic acid was dissolved (about 10-15 minutes). The reactor was then charged with 28.8 Kg of chloroform and stirred for about 5 minutes. 132 grams of Bpheide (216 mmol) was then added to the mixture which was then stirred at 35°C. A palladium acetate solution in chloroform was prepared in a separate vessel by adding 4 Kg of chloroform and 243.1 gram (1.08 mol) of palladium acetate to the vessel. The mixture was stirred until all the palladium acetate was dissolved. The palladium acetate solution was added to the 50 L reactor for 15 minutes while stirring vigorously under N2 blanketing. After all the palladium acetate solution was added, the mixture was stirred under N2 at 34°C-36°C for an additional 15 minutes. While stirring, 600 ml of water was added into the reaction mixture. The solution was cooled to 20°C.

[0099] The palladium black precipitate formed in the reaction mixture was filtered through a lOp cotton cartridge connected to a 0.2pTeflon capsule filter using a Teflon diaphragm pump. The filtrate was collected in a 150 L stirred tank containing 65.4 liters of water and 9.9 Kg of chloroform. After filtration was completed, the 50 L reactor was washed with 9.9 Kg of chloroform. The chloroform used for washing was filtered through the same filter used for filtration of the palladium black. The filtered chloroform was combined with the previous filtrate. The mixture of filtrates was stirred gently for about 15 minutes under N2 blanketing, then kept unstirred for 30 minutes whereby the phases of the mixture separated.

[0100] The layers were separated by transferring the chloroform (bottom layer) solution into a reactor. The chloroform solution was vacuum distilled at about 50°C while stirring the solution. The solvent was distilled off until the volume of the slurry was about 130 ml / lg Bpheide. After reaching the desired volume, the solution was heated to 55°C, at atmospheric pressure and then stirred for 10 minutes.

[0101] The solution was then cooled to 10 C for at least 3 hours while stirring slowly under N2 blanketing and then stirred at 10°C for an additional 1 hour. The obtained slurry was filtered through a 0.45p Teflon membrane. The filtered product was washed with 550 ml of cold (~5°C) chloroform. The filter cake was dried by an N2 flow for about 15 minutes then dried overnight in a vacuum oven at 40°C while maintaining a slow flow of N2 through the oven.

[0102] 121 grams of Pd-Bpheide was obtained.

[0103] EXAMPLE 3 - Preparation of padeliporfin

[0104] An exemplary experimental procedure for producing padeliporfin is described as follows:

[0105] A nitrogen flushed 10-liter reactor was charged with 3.5 liter of DMF and heated to 50°C under N2 atmosphere. The reactor was then charged with 100 gr (140 mmol) of Pd-Bpheide. The contents of the reactor were then stirred for 10-15 minutes. In a separate vessel, a solution of 106 grams of KOH and 212 grams of taurine were dissolved in 450 ml of water. The KOH / Taurine solution was added over 5-10 minutes to the DMF / Pd-Bpheide solution. The combined solution was stirred for 3.5 hours at 50°C under N2 atmosphere.

[0106] A 30-liter reactor was charged with 20 liters of acetone and heated to 50°C while maintaining an N2 atmosphere. 2.5 liters of water was added to the 10-liter reactor. The contents of the 10-liter reactor were stirred for 3-5 minutes and then transferred into the 30- liter reactor under N2 atmosphere. The 10-liter reactor was washed with 2.5 liters of water which was then transferred into the 30-liter reactor. The 30-liter reactor was then stirred at 50°C for 10-15 minutes under N2 atmosphere. The 30-liter reactor was then cooled to 18-20°C over a 3-hour period while stirring to obtain a slurry. The slurry was filtered over a lOp membrane. The crude filtered product was washed with a solution of 800 ml acetone and 200 ml water. The product was then washed with 10 liters of hot (50°C) acetone. Crude padeliporfin was obtained by drying the product overnight at room temperature in a vacuum oven under N2 atmosphere. The crude padeliporfin was then suspended in acetone. 0.13 liters of acetone per 1 gram of crude padeliporfin was used. The solution was refluxed for 25-30 minutes, after which the hot slurry was filtered. 33 ml of hot (50°C) acetone per gram of crude padeliporfin was used to wash the filter cake. The resulting padeliporfin was dried in a vacuum oven at 40°C for 48-72 hours.

[0107] The molar yield of padeliporfin obtained was 91% with a purity greater than 96%.

[0108] While the present subject matter has been shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that many alternatives, modifications and variations may be made thereto without departing from the spirit and scope thereof. Accordingly, it is intended to embrace all such alternatives, modifications, and variations that fall within the spirit and broad scope of the claims.

[0109] All publications, patents and patent applications mentioned in this specification are herein incorporated in their entirety by reference into the specification, to the same extent as if each individual publication, patent or patent application was specifically and individually indicated to be incorporated herein by reference.

Claims

CLAIMS1. A process for the preparation of an alkali metal salt comprising one or more monovalent alkali metal cations of the compound of Formula (I),the process comprising the step of reacting palladium-bacteriopheophorbide (Pd-Bpheide) of Formula (II) with taurine and a baseCD wherein the base is a non-nucleophilic base comprising a monovalent cation, and wherein the base has a pKa of at least 10.

2. The process of claim 1, wherein the base is selected from a group consisting of sodium hydroxide, sodium carbonate, potassium hydroxide and potassium carbonate.

3. The process of claim 2, wherein the base is potassium hydroxide.

4. The process of any one of claims 1-3, wherein the process is carried out in the presence of a polar aprotic solvent selected from a group consisting of dimethyl formamide (DMF), N-methyl pyrrolidone (NMP), dimethysulfoxide (DMSO), N,N'- dimethylpropyleneurea (DMPU), Sulfolane, or combinations thereof.

5. The process of claim 4, wherein said polar aprotic solvent is DMF.

6. The process of any one of claims 1-5, further comprising a step of isolating the compound of Formula (I) from the reaction mixture comprising (i) adding acetone and water to precipitate the compound of Formula (I) from the mixture; and (ii) filtering the precipitated padeliporfin salt.

7. The process of any one of claims 1-6, wherein the reaction is carried out at a temperature of between 40 C and 60 C.

8. A process for the preparation of palladium-bacteriopheophorbide (Pd-Bpheide) of Formula (II),the process comprising the step of reacting a solution comprising Bpheide of Formula (III), ascorbic acid and a solvent mixture comprising at least one C1-C4 alcohol and at least one chlorinated organic solvent, with a palladium reagentwherein the at least one C1-C4 alcohol is selected from a group consisting of methanol, ethanol, n-propanol, isopropanol, butanol, 2-butanol, isobutanol or any combinations thereof; wherein the at least one chlorinated organic solvent is selected from a group consisting of chloroform, dichloromethane, tetrachloromethane, 1,1 dichloroethane, 1,2 dichloroethane, 1,1,2 trichloroethane, 1,1,1 trichloroethane, 1,1, 1,2 tetrachloroethane, pentachloroethane, hexachloroethane, 1,2 dichloropropane, chlorobenzene, 1,2 dichlorobenzene and 1,4 dichlorobenzene or any combination thereof, and wherein the volumetric ratio of alcohol to chlorinated organic solvent is between 1:0.5 and 1:3.

9. The process of claim 8, wherein the palladium reagent is palladium acetate or palladium chloride.

10. The process of claim 8, wherein the solvent mixture comprises methanol and chloroform.

11. The process of claim 8, wherein the volumetric ratio of alcohol to chlorinated organic solvent is 1:1.

12. The process of any one of claims 8-11, wherein the molar ratio of palladium acetate to ascorbic acid is between 1:5 and 1:15.

13. The process of claim 12, wherein the molar ratio of palladium acetate to ascorbicacid is 1:9.

14. The process of any one of claims 8-13, wherein the molar ratio of palladium acetate to Bpheide is between 1:0.1 and 1:1.

15. The process of claim 14, wherein the molar ratio of palladium acetate to Bpheide is 1:0.2.

16. The process of any one of claims 8-15, wherein the ratio of chlorinated organic solvent to Bpheide is between 75 ml / 1 gram and 500 ml / 1 gram.

17. The process of claim 16, wherein the ratio of chlorinated organic solvent to Bpheide is 167 ml / 1 gram.

18. The process of any one of claims 8-17, further comprising a step of isolating the compound of Formula (II) from the reaction mixture comprising (i) filtering palladium black from the mixture; (ii) distilling the solvent from the mixture; and (iii) filtering the precipitated Pd-Bpheide.

19. The process of any one of claims 8-18, wherein the reaction is carried out at a temperature of between 25°C and 50°C.

20. The process of claim 19, wherein the reaction is carried out at a temperature of between 30°C and 40°C.

21. A process for the preparation of an alkali metal salt comprising one or more monovalent alkali metal cations of the compound of Formula (I),the process comprising the following steps: c) reacting a solution comprising Bpheide of Formula (III), ascorbic acid and a solvent mixture comprising at least one C1-C4 alcohol and at least one chlorinated organic solvent, with a palladium reagentto obtain Pd-Bpheide of Formula (II)(II); and d) reacting palladium-bacteriopheophorbide (Pd-Bpheide) of Formula (II) with taurine and a base, wherein the base is a non-nucleophilic base comprising a monovalent cation, and wherein the base has a pKa of at least 10.

22. The process of claim 21, wherein the palladium reagent is palladium acetate or palladium chloride.

23. The process of claim 21 or 22, wherein the solvent mixture comprises at least one Cl- C4 alcohol selected from a group consisting of methanol, ethanol, n-propanol, isopropanol, butanol, 2-butanol, isobutanol or any combinations thereof; and at least one chlorinated organic solvent selected from a group consisting of chloroform, dichloromethane, tetrachloromethane, 1,1 dichloroethane, 1,2 dichloroethane, 1,1,2 trichloroethane, 1,1,1 trichloroethane, 1,1, 1,2 tetrachloroethane, pentachloroethane, hexachloroethane, 1,2 dichloropropane, chlorobenzene, 1,2 dichlorobenzene and 1,4 dichlorobenzene or any combination thereof.

24. The process of claim 23, wherein the solvent mixture comprises methanol and chloroform.

25. The process of any one of claims 21-24, wherein the volumetric ratio of alcohol to chlorinated organic solvent is between 1:0.5 and 1:3.

26. The process of claim 25, wherein the volumetric ratio of alcohol to chlorinatedorganic solvent is 1:0.5.

27. The process of any one of claims 21-26, wherein the molar ratio of palladium acetate to ascorbic acid is between 1:5 and 1:15.

28. The process of claim 27, wherein the molar ratio of palladium acetate to ascorbic acid is 1:9.

29. The process of any one of claims 21-28, wherein the molar ratio of palladium acetate to Bpheide is between 1:0.1 and 1:1.

30. The process of claim 29, wherein the molar ratio of palladium acetate to Bpheide is 1:0.2.

31. The process of any one of claims 21-30, wherein the ratio of chlorinated organic solvent to Bpheide is between 75 ml / 1 gram and 500 ml / 1 gram.

32. The process of claim 31, wherein the ratio of chlorinated organic solvent to Bpheide is 167 ml / 1 gram.

33. The process of any one of claims 21-32, further comprising an intermediate step between step a) and step b) of isolating the compound of Formula (II) from the reaction mixture of step a) comprising (i) filtering palladium black from the mixture;(ii) distilling the solvent from the mixture; and (iii) filtering the precipitated Pd- Bpheide.

34. The process of any one of claims 21-33, wherein the reaction of step a) is carried out at a temperature of between 25 C and 50°C.

35. The process of claim 34, wherein the reaction of step a) is carried out at a temperature of between 30°C and 40°C.

36. The process of any one of claims 21-35, wherein the base is selected from a groupconsisting of sodium hydroxide, sodium carbonate, potassium hydroxide and potassium carbonate.

37. The process of claim 36, wherein the base is potassium hydroxide.

38. The process of any one of claims 21-37, wherein the process is carried out in the presence of a polar aprotic solvent selected from a group consisting of dimethyl formamide (DMF), N-methyl pyrrolidone (NMP), dimethysulfoxide (DMSO), N,N'- Dimethylpropyleneurea (DMPU), Sulfolane, or combinations thereof.

39. The process of claim 38, wherein said polar aprotic solvent is DMF.

40. The process of any one of claims 21-39, further comprising a step after step b) of isolating the compound of Formula (I) from the reaction mixture of step b) comprising (i) adding acetone and water to precipitate the compound of Formula (I) from the mixture; and (ii) filtering the precipitated padeliporfin salt.

41. The process of any one of claims 21-40, wherein the reaction of step b) is carried out at a temperature of between 40°C and 60°C.

42. The process of any one of claims 1-7 or 21-41, wherein said cations are selected from a group consisting of K+, Na+, and Li+.

43. The process of claim 42, wherein the compound of Formula (I) is padeliporfin dipotassium salt.

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