On August 8, 2014, 3SBio (NASDAQ: SSRX) in-licensed leukotuximab from DiNonA, a Korean biopharma. Leukotuximab is an anti-JL1 antibody for the treatment of JL1 positive acute leukemia including ALL and AML. Leukotuximab has entered into an open label and dose-escalating phase I trial in June 2014 in Korea. 3SBio will make upfront and milestone payments, plus sales-based royalty. Additional terms of the license are not being disclosed.
JL1 is a differentiation antigen strongly and specifically expressed on stage II double positive (CD4+CD8+) human cortical thymocytes. The expression of JL1 antigen was observed in 75.6% of leukemic cases. This antigen was not expressed on mature peripheral blood cells or other normal tissues. Thus, anti-JL1 mAb may have potential for the treatment of leukemia.
In 2011, DiNonA reported that JL1 is a specific epitope on CD43. An anti-JL1 mAb, known as YG5, interacted with a non-glycosylated epitope of the human CD43 extracellular domain. In in vivo leukemia model, both anti-JL1 mAb and JL1-saporin antibody-drug conjugate induced effective cytotoxicity in tumor cells and prolonged survival.
According to 3SBio, there are 30,000-40,000 newly diagnosed acute leukemia patients each year in China. Patients are currently treated with traditional chemotherapy and bone marrow transplant, both of which have major side effects. Since JL1 is selectively expressed on the surface of human leukaemic cells, leukotuximab can be an excellent targeted treatment for the JL1 positive acute leukemia.
The R&D of anti-CD43 mAb has not gone smoothly. In June 2010, Pfizer withdrew Mylotarg (gemtuzumab ozogamicin) from the market at the request of the FDA. This drug is an anti-CD43 mAb linked to a cytotoxic agent. It was approved for the treatment of AML under the accelerated approval program. However, it didn’t demonstrate an improvement in clinical benefit when adding to standard chemotherapy.
Is leukotuximab better than Mylotarg? Further assessment in clinical trials is warranted.
About 3SBio Inc.
3SBio is a China-based biotechnology company focused on developing and marketing biological products in China. In February 2007, 3SBio raised $123.2 million with an IPO on the NASDAQ. 3SBio has launched four biological products: Epiao (rhEPO), Tpiao (rhTPO), Intefen (TNFα-2a) and Inleusin (rhIL-2). Total net revenues in 2012 were RMB 669.9 million (372.9 million from Epiao and 210.4 million from Tpiao).
 J Exp Med. 1993, 178(4), 1447-1451.
 Leukemia. 1998, 12(10), 1583-1590.
 Cancer Immunol Immunother. 2011, 60(12), 1697-1706.
 Immune Netw. 2014, 14(3), 164-170.