PRO 140—a receptor antibody for HIV
PRO 140 is the name given to an antibody designed to interfere with HIV’s ability to attach itself to the CCR5 receptor. PRO 140 works in a slightly different manner than maraviroc. Importantly, the antibody does not affect the functioning of the CCR5 receptor. This may mean that PRO 140 does not have any effects on the health of the immune system and its ability to fight infections. Because PRO 140 achieves its anti-HIV effects in a manner different from maraviroc, it may have potential for use in people for whom maraviroc no longer works.
Initial enthusiasm for PRO 140 was guarded because the drug needed to be given intravenously every two weeks. In an era when most anti-HIV medications are taken orally, intravenous treatment would not be a preferred choice for patients or their doctors. However, the developer of PRO 140, Progenics Pharmaceuticals Inc., has created a new formulation of this drug that can be given by injection under the skin (subcutaneous injection). These injections would need to be done once every two weeks and could be done at home—a possibility that improves prospects for the drug.
In placebo-controlled studies with 39 symptom-free HIV positive people, infusions of PRO 140 at a dose of about 5 mg/kg of body weight have been able to suppress HIV production by at least 1.83 logs and, in some cases, as much as 2.5 logs. These differences may seem small but when it comes to suppressing the production of HIV, every bit counts.
Ten days after a PRO 140 infusion, HIV levels in the blood began to rise, suggesting that the antibody’s effect was waning when given as the sole anti-HIV agent.
PRO 140 was not associated with any serious side effects.
CD4+ cell counts increased by about 29%, or about 130 cells, in volunteers given the drug and remained elevated for up to three weeks after the injection.
Hopefully regulatory authorities will approve the testing of the new injectable formulation of PRO 140 for larger clinical trials in the months ahead.
Jacobsen JM, Tompson M, Saag MS, et al. Antiretroviral activity and pharmacodynamics of PRO 140, a CCR5 monoclonal antibody, in HIV-infected individuals. Program and abstracts of the 47 Interscience Conference on Antimicrobial Agents and Chemotherapy, 17 – 20 September 2007, Chicago, USA. Abstract H-716.