Protein Design Labs (PDL) has started Phase I clinical trialswith its humanized therapeutic monoclonal antibody (MAb) foracute myelogenous leukemia and chronic myelogenousleukemia.

The trials will be conducted by David Scheinberg andcolleagues at the Memorial Sloan-Kettering Cancer Center inNew York.

The PDL antibody, SMART M195, is "90 percent human and 10percent mouse," said Peter Dworkin, PDL 's (NASDAQ:PDLI)director of corporate communications. The mouse portion isthe antibody's complimentarity determining region (CDR), orits binding site. Scientists at the Mountain View, Calif.,company used computer modeling to ensure that their antibodywould bind well to its target receptor.

Scientists hope that patients will not suffer an immuneresponse to humanized monoclonals, as happens when humansare injected with antibodies derived from mice.

At least one humanized therapeutic antibody, named coinedCAMPATH1, directed against B cells and T cells, has beenproven safe in limited human studies. CAMPATH1, to whichBurroughs Wellcome of Research Triangle Park, N.C., holds therights, was developed at the Medical Research Council inCambridge, England.

Clinical safety studies of another of PDL's humanizedantibodies -- an anti-Tac antibody for treating graft-vs.-hostdisease, organ transplant rejection and certain autoimmunediseases -- are complete and should be announced by the end ofthis year, Laurence Jay Korn, PDL's president and chiefexecutive, told BioWorld.

The company already knows that in their totally mouseconfigurations the two antibodies work in patients. "Both aresafe and efficacious in clinical trials, but they are limited bythe HAMA (human anti-mouse antibody) response," said Korn.

-- Jennifer Van Brunt BioWorld Staff

(c) 1997 American Health Consultants. All rights reserved.