The United States of America, As Represented by the Secretary, Department of Health and Human Services

Yen T Phung

Wei Gao

Mitchell Ho

Yifan Zhang

Ira H Pastan

Raffit Hassan

Described herein is the use of rabbit hybridoma technology, along with a panel of truncated mesothelin domain fragments, to identify anti-mesothelin mAbs that bind specific regions of mesothelin. In one aspect of the present disclosure, the rabbit mAbs bind an epitope that is not part of Region I. In particular, the identified mAbs (YP187, YP223, YP218 and YP3) bind either Region II (391-486), Region III (487-581) or a native conformation of mesothelin with subnanomolar affinity. These antibodies do not compete for binding with the mesothelin-specific immunotoxin SS1P or mesothelin-specific antibody MORAb-009. In another aspect, disclosed is a high-affinity rabbit mAb that binds Region I of mesothelin (YP158). YP158 binds native mesothelin protein in cancer cells and tissues with high affinity and specificity.

Mesothelin domain-specific monoclonal antibodies and use thereof

Described herein is the identification of a panel of high affinity monoclonal antibodies that bind GPC3. The disclosed antibodies recognize native GPC3 on the surface of cancer cells, as well as soluble GPC3. The highest affinity antibody (YP7) was further characterized and shown to be highly sensitive in that it was capable of detecting cancer cells with low expression of GPC3. YP7 also exhibited significant HCC tumor growth inhibition in vivo. Immunotoxins comprising the antibodies disclosed herein fused to PE38 exhibited very high binding affinity for GPC3-expressing cells and significantly inhibited GPC3-expressing cancer cell growth. Thus, the high-affinity monoclonal antibodies disclosed herein can be used for the diagnosis and treatment of GPC3-expressing cancers.

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Annandale, VA, United States of America

Yen T Phung