Long-acting antiretrovirals could provide a useful alternative to daily oral therapy for HIV-1 infected individuals. However, the need for combination therapy and the potential for multiple IV/IM injections or tolerability issues may create roadblocks to this type of therapy. Adnectins are small proteins derived from the 10th type III domain of the human fibronectin protein that possess modifiable binding loops akin to the complementarity determining region of an antibody. Using Adnectins, we have developed the Combinectin inhibitor BMS-986197, a long-acting biologic with 3 independent and synergistic modes of HIV entry inhibition that potentially could be self-administered as a long-acting subcutaneous injection.
Adnectins targeting CD4 and a region of gp41 were isolated and optimized for antiviral potency and biophysical characteristics. The anti-gp41 Adnectin was joined at its amino terminus to the anti-CD4 Adnectin via a peptide linker. A third inhibitor, an alpha-helical peptide fusion inhibitor, was linked to the carboxy end of the anti-gp41 Adnectin via another linker. Finally, a human serum albumin (HSA) molecule was attached to amino terminus of the anti-CD4 Adnectin to optimize in vivo PK.
The EC50s of the isolated anti-CD4 Adnectin, anti-gp41 Adnectin, and fusion inhibitor peptide were 8.5 nM, 5.4 nM, and 0.4 nM, respectively. Various synergies were obtained through linking all three inhibitors into a single molecule. Optimally combining the two Adnectins increased potency over 100-fold to ~30 pM. Addition of the fusion inhibitor peptide resulted in an increased resistance barrier compared to the separate components, as virus resistant to any one of the three components did not affect the potency of BMS-986197. Addition of HSA to the amino terminus decreased potency to 0.27 nM, but improved PK, as subcutaneous dosing in a cynomologous monkey model produced a t1/2 of 30 h. BMS-986197 has the biophysical characteristics and expression levels in stable cell lines compatible for further drug development, with a projected weekly subcutaneous human dose.
BMS-986197 is a novel recombinant biologic molecule containing three independent HIV inhibitors that has been developed as a potential single long-acting regimen for HIV-1. This molecule has the biophysical characteristics amenable for a self-administered subcutaneous weekly injection.