Despite advances in the development of HIV drugs there remains a need for new therapies. Toxicities associated with long term use of many of the approved HIV drugs coupled with the development of resistance drives the need for new and novel antivirals. Maturation inhibitors (MIs) represent one such class of HIV therapies. HIV maturation inhibitors block virus replication by disrupting the conversion of the capsid precursor protein, CA-SP1 (p25), to the mature form of capsid, CA (p24) resulting in the formation of non-infectious viral particles. Unlike protease inhibitors that bind to and inhibit the action of the vral protease, MIs directly target the HIV-1 Gag protein. This novel mechanism of action allows MIs to retain full activity against viruses that have developed resistance to approved classes of HIV drugs. Clinical proof-of-concept for maturation inhibitors was established with the first-in-class MI, bevirimat (BVM). In a series of trials, BVM was shown to be safe and effective in reducing HIV viral load in infected individuals, however, a lack of uniform patient response was also observed. Analysis of patient virus revealed that a single amino acid polymorphism in the SP1 region of the viral Gag protein was a primary determinant of patient response. This polymorphism involves a Val to Ala change at SP1 amino acid 7: V7A. Approximately 50% of HIV-1 isolates contain V7 and are highly sensitive to BVM while the remaining 50% contain A7 and lack sensitivity. As a result of this observation, clinical development of BVM was terminated. DFH Pharma is focusing on the identification of next generation MIs with broad anti-HIV activity including BVM-resistant isolates. This work has led to the discovery of bevirimat analogs that are highly active against both BVM-sensitive virus and those exhibiting polymorphic-mediated resistance. While similar in structure to bevirimat, these 2nd generation MIs are modified at the C-28 position. The most potent of the newly identified inhibitors exhibit nM IC50 values against both BVM-sensitive virus and resistant A7 polymorphs. The enhanced activity against the A7 virus exhibited by these compounds represents a 100-fold increase in over that observed with BVM. Importantly, efforts to date suggest that these 2nd generation MIs will retain the promising drug development profile observed with bevirimat. The goal of the proposed research is to continue the identification of 2nd generation MIs suitable for advancement as drug development candidates. Specifically, DFH Pharma will;i) continue to identify 2nd generation MIs with potent activity against the broad spectrum of HIV isolates, ii) characterize the development profiles of the most promising 2nd generation MIs and iii) select a drug development candidate to advance into pre-clinical studies.
Despite advances in the development of HIV drugs there remains a need for new therapies. Maturation inhibitors represent one class of new HIV therapies. DFH Pharma is focusing on the identification of a new generation of maturation inhibitors for development as HIV therapeutics.