CytoDyn Inc.’s (CYDY) PRO 140 is One of the Most Promising Monoclonal Antibody Therapies

New forms of treatment based on monoclonal antibodies show a lot of promise for human immunodeficiency virus patients with drug resistance or limited treatment options, according to HIV/AIDS researchers at this year’s edition of the Conference on Retroviruses and Opportunistic Infections (CROI 2017), which was held last month in Seattle ( Researchers focused on two monoclonal antibody therapies – PRO 140 from CytoDyn Inc. (OTCQB: CYDY) and Ibalizumab from TaiMed Biologics, both of which have shown impressive results during clinical trials as long-acting therapies for HIV patients with limited options because of HIV drug resistance.

PRO 140 is currently in two Phase 3 clinical trials and has several potential benefits compared to regular HIV therapies, including minimal side effects, hardly any toxicity, and less frequent dosing. Part of a new class of therapeutics designed to protect healthy cells from viral infection, PRO 140 in its current form is administered by weekly subcutaneous injection, and all of the research so far has indicated that it can maintain viral suppression for a long time (current patients on PRO 140 single agent therapy are going more than two years). PRO 140 works by blocking one of the two co-receptors the human immunodeficiency virus uses to enter cells – CCR5. It is estimated that about 70 percent of HIV patients in the United States and Europe and up to 90 percent of newly diagnosed cases carry a CCR5-using form of the virus (R5 strain of HIV).

Details of the innovative therapy, which has been granted fast track candidate status by the U.S. Food and Drug Administration, were presented at CROI 2017 by Amarex Clinical Research’s Dr. Kush Dhody, who oversees CytoDyn’s clinical trials. An early study of PRO 140 and its effects showed that a single IV infusion generated significant antiviral activity, while a follow-up study showed that weekly subcutaneous PRO 140 injections also reduced viral load exponentially. Most of the findings presented at the CROI Conference came from an extension study of a Phase 2b trial that looked into PRO 140 being used as a single agent maintenance therapy for patients with viral suppression after following standard combination antiretroviral therapy.

The study included a total of 42 patients, all of them with CCR5-tropic HIV, who were on stable antiretroviral therapies with undetectable viral load. Participants received weekly subcutaneous injections of PRO 140 for one week only while being on their regular treatments. After the first week, the patients continued only with PRO 140. Twenty-two participants of the 42 maintained viral suppression throughout the main course of the study (12 weeks).  From the 16 patients who were given the option to continue with this therapy in an extension arm, 11 are still on this therapy.

Dhody explained that 13 of these 16 patients (or 81 percent) maintained viral suppression for more than 40 weeks. Ten of these (63 percent) maintained suppression for more than two years and were still undergoing PRO 140 monotherapy at the time when the results of the study were released. Of the other patients, five experienced viral rebound after 100 to 700 days, while one person moved away and no longer participated in the study. As for side effects, PRO 140 was safe and well tolerated by patients, with no serious adverse reactions reported.

The results of the study are very encouraging, researchers said, and they support the continued development of this therapy as a single-agent, long-acting treatment for HIV patients who are not satisfied with the quality of life they have with regular antiretroviral therapies as they experience toxicity, intolerance or resistance to them. Maintenance monotherapy with PRO 140 is currently being studied in a larger clinical trial (a Phase 3), as researchers are trying to identify which factors may predict good treatment response.

The other monoclonal antibody therapy discussed at CROI 2017, Ibalizumab, showed modest antiviral activity when administered via IV infusion every two weeks, together with optimized antiretroviral therapy. Compared to PRO 140, Ibalizumab is effective against HIV that uses either CCR5 or CXCR4 co-receptors.

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