Anti-p-selectin antibodies and methods of their use and identification

Abstract

Antibodies are disclosed which bind specifically to P-selectin and which block the binding of PSGL-1 to P-selectin. These anti-P-selectin antibodies may also cause dissociation of preformed P-selectin / PSGL-1 complexes. The disclosure identifies a heretofore unrecognized, near N-terminal, antibody binding domain (a conformational epitope) of P-selectin to which the function-blocking antibodies (which may be chimeric, human or humanized antibodies for example) bind. Antibodies are disclosed which bind to the conformational epitope of P-selectin and which have a dual function in blocking binding of PSGL-1 to P-selectin, and in causing dissociation of preformed P-selectin / PSGL-1 complexes. Such single and dual function anti-P-selectin antibodies and binding fragments thereof may be used in the treatment of a variety of inflammatory and thrombotic disorders and conditions. Screening methods for identifying such antibodies are also disclosed.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application is a continuation-in-part of U.S. Ser. No. 12 / 516,987, filed May 29, 2009, which claims priority under 35 U.S.C. 371 from International Application No. PCT / US2007 / 024692, filed Nov. 30, 2007, which claims benefit of U.S. Provisional Application No. 60 / 872,170, filed Dec. 1, 2006. Each of the above applications is hereby expressly incorporated herein by reference in its entirety.STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT[0002]Not applicable.BACKGROUND[0003]The present invention relates to antibodies and antibody fragments which bind to specific conformational epitopes of P-selectin, and to methods of their use and identification.[0004]In normal hemostasis and immune surveillance, leukocytes circulate freely in the blood and respond to injury and infection in a sequential process of adhesion signaling mediated by cell adhesion molecules (1-3). In inflammatory and thrombotic disease, this process is dysr...

AI Technical Summary

Benefits of technology

[0024]In SCD, as noted above, interactions between sickled red cells, platelets, leukocytes and the microvasculature are P-selectin-dependent processes and result in vasoocclusion and painful crisis. Studies in transgenic mice engineered to express human β hemoglobin S (βs) have shown that antibody-mediated inhibition of P-selectin function can prevent and / or reduce vasoocciusion, indicating a therapeutic potential for this target. In addition mice expressing the βs hemoglobin that lack P-selectin (due to gene deletion) do not suffer vasoocciusion, further supporting a key role for this molecule in this morbidity.

[0025]The hyper-inflammatory state in SCD patients is characterized by activated monocytes and vascular endothelium (61-63). A similar pro-inflammatory phenotype was demonstrated in resting state βs mice which exhibit elevated levels of peripheral leukocytes and neutrophils, an increased number of rolling and adherent leukocytes, and reduced blood flow volume and red blood cell velocities (64). The βs mice were hypersensitive to hypoxia / reoxygenation resulting in an inflammatory response represented by a significant increase in the number of adherent and emigrated leukocytes. This inflammatory response was completely blocked by a functionally blocking anti-mouse P-selectin antibody, but not by a functionally blocking anti-mouse E-selectin antibody, demonstrating a critical role for P-selectin in this process.

Problems solved by technology

In inflammatory and thrombotic disease, this process is dysregulated and can sustain pathology wherein leukocytes attack the body's own tissue and can cause serious and sometimes deadly complications.

Hb β-thalassemia variants (resulting in the inability to produce the normal βA globin chain (βo) or a reduction in its production (β+) result in a range of clinical severities.

Despite the capacity to determine genetic risk factors, the ability to predict disease course from birth is limited (27).

However, it has recently become clear that hemoglobin S polymerization is not solely responsible for vasoocclusion.

Long-term repeated vasoocclusive events and occlusions occurring in the macrovasculature can cause life-threatening complications leading to organ damage and failure, stroke and death (40).

Sickled red cells can become trapped in the spleen causing it to become enlarged and precipitating splenic sequestration crisis causing sudden and severe anemia.

Severe pain resulting from vasoocclusive crisis can be treated with narcotics but their use is controversial due to concerns of narcotic addiction and tolerance.

Other complications with narcotic use are drug-seeking behavior, sedation and respiratory depression.

Oxygen management has been utilized to treat vasoocclusive pain crisis despite the lack of strong evidence supporting its effectiveness.

Bone marrow transplantation may be considered and can be curative, but its use is restricted to a limited number of patients, and carries a high risk of morbidity and mortality (22).

In summary, most therapies for vasoocclusive pain crisis in SCD patients provide symptomatic relief and do not address the underlying cause of this debilitating condition.

To date only one therapy has been approved by the FDA for the treatment of pain crisis, thus, patients with SCD represent a major unmet medical need in a life-threatening disease with severe morbidities.

In SCD, as noted above, interactions between sickled red cells, platelets, leukocytes and the microvasculature are P-selectin-dependent processes and result in vasoocclusion and painful crisis.

Nevertheless, differentiating UC from CD, as well as other types of inflammatory conditions of the intestines, such as irritable bowel syndrome, infectious diarrhea, rectal bleeding, radiation colitis, and the like, is difficult, because the mucosa of the small and large intestines reacts in a similar way to a large number of different insults.

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