A novel monoclonal antibody-based therapeutic designed byMedarex Inc. has been shown to neutralize the humanimmunodeficiency virus (HIV) and inhibit infection of healthyimmune cells, according to an article in the July issue of TheJournal of Infectious Diseases.

In vitro studies conducted by an independent French researchteam revealed that a monoclonal antibody therapeutic, knownas a bispecific antibody, inhibited HIV infection of macrophagesand other immune cells, including CD4 receptor-bearing cellsthat can serve as reservoirs for the HIV virus, which causesAIDS.

In humans, naturally occurring antibodies use a "target-trigger"mechanism to fight viruses and foreign pathogens. Theseantibodies target and bind to the pathogen, then bind to aspecific receptor found on the surface of macrophages, knownas an Fc receptor, which triggers an immune response todestroy the targeted pathogen. Conventional mousemonoclonal-based therapeutics cannot efficiently bind to Fcreceptors and trigger killing of the pathogen by macrophages.

Medarex's bispecific antibody is a combination of twoantibodies linked together that replicate the target-triggermechanism used by natural antibodies. While the targetantibody binds to a virus or foreign pathogen, Medarex'sTrigger antibody binds to an Fc receptor on immune cells moreefficiently than natural antibodies.

The bispecific antibody was also shown to be more efficient inneutralizing HIV than the single MAb directed against the gp41 protein. When used alone, the gp 41 antibody failed toprovide any protection against HIV infection of macrophages.

"We think the bispecific antibody causes macrophages to ingestthe AIDS virus," said Donald L. Drakeman, president and chiefexecutive officer of Princeton, N.J.-based Medarex.

"This study further validates our bispecific antibody'stherapeutic potential in treating HIV infection," Drakeman said."The therapeutic not only prevents infection of healthyimmune cells, but it also appears to be able to destroy HIV byenhancing the body's own immune system."

He said the company is working toward entering human clinicaltrials in six to 12 months.

Drakeman said Medarex's bispecific antibody also has potentialas a cancer treatment-- initially for ovarian and breast cancer -- as a vaccine and as a vaccine adjuvant.

At a report last week in Brindisi, Italy, Edmund J. Gosselin ofthe Department of Microbiology at Dartmouth Medical School,said tetanus vaccines containing the vaccine adjuvant wereshown to increase the production of T cells by more than 200times compared with the number of T cells produced inresponse to the tetanus virus itself.

The company's stock (NASDAQ:MEDX) was up $2 on Tuesday at$10.25.

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