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# CytoDyn Orphan Drug Request Rejected by FDA
- URL: https://www.fdaweb.com/cytodyn-orphan-drug-request-rejected-by-fda/
- Published: 2017-04-17T12:00:00.000Z
- Updated: 2026-09-14T22:18:07.000Z
- Author: David McFarland
- Tags: Drugs, #legacy-id-D5138461

FDA has denied a CytoDyn request for an orphan drug designation (ODD) for PRO 140 because the therapy appears to have the potential to treat more than just the subset of multi-drug resistant HIV patients for which the designation was requested. CytoDyn is currently conducting a pivotal Phase 2b/3 trial with PRO 140 in combination with other antiretroviral agents in the patient population submitted to FDA in the ODD application. Additionally, CytoDyn is conducting a 300-patient Phase 2b/3 trial with PRO 140 as a single-agent maintenance therapy for HIV-infected patients which is a U.S. patient population that far exceeds the 200,000-patient threshold for ODD, according to the company.

  
PRO 140 belongs to a new class of HIV/AIDS therapeutics called viral-entry inhibitors that are intended to protect healthy cells from viral infection. It is a humanized IgG4 monoclonal antibody directed against CCR5, a molecular portal that HIV uses to enter T-cells. “PRO 140 blocks the predominant HIV (R5) subtype entry into T-cells by masking this required co-receptor, CCR5,” the company says.