Background: Elpida® / Elsulfavirine (VM1500) is the prodrug of VM1500A, a new potent non-nucleoside reverse transcriptase inhibitor with unique pharmacokinetic properties (T1/2 ~ 9 days). A 20 mg once daily dosing was chosen for further study based on 12-week efficacy, pharmacology and safety data; 48 week data comparing Elpida 20 mg to Efavirenz-based therapy plus tenofovir/emtracitabine (TDF/FTC) has been reported effective and safe. The objective of this study was to assess the efficacy and safety of an ART regimen including Elpida 20 mg plus two NRTI during 96 weeks.
Methods: In the parent Phase IIb randomized, double-blind, multicenter study, ART-naïve HIV-1-infected patients, treated initially for 48 weeks with Elpida plus TDF/FTC, continued the study treatment for up to 96 weeks. During this period they received Elpida 20 mg and various two NRTI regimens.
Results: After initial 48 weeks of treatment, 81% of patients on Elpida 20 mg and 73.7% patients on Efavirenz had VL < 50 c/mL (MITT). A total of 81out of 87 (93%) patients, treated with Elpida in the main study, continued in the follow-up study for additional 48 weeks. A total of 73 out of 87 (84%) patients had VL < 50 c/mL and 79/87 (91%) had < 400 c/mL at week 96. 3 patients receiving Elpida had VL >1000 c/mL during the study, presumably due to poor compliance; none had NNRTI resistance mutations. A CD4+ T-lymphocyte count increased by 246 ± 175.3 cells/mm3 during 96 weeks of treatment. Median CD4/CD8 ratio increased from 0.40 to 0.82. There were no new significant AEs, related to Elpida, after 48 weeks of treatment. New AE were mainly related to the changes of two NRTI regimen, including 2/89 (2.2%) patients with Grade 3 events (i.e. decreased appetite, irritability, dyspnea and rash). No drug-related SAE were reported. Total exposure to Elpida was 151.7 patient-years.
Conclusions: This study demonstrated that Elpida was safe and well tolerated to 96 weeks, with continued virologic efficacy, immunologic improvement and favorable resistance profile. Elpida-based therapy is a safe and effective long term strategy with many potential advantages over current therapies.

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