Treatment-Naïve Adults Phase 3 Randomized, Controlled, Clinical Trial of Bictegravir Coformulated With FTC/TAF in a Fixed-Dose Combination vs Dolutegravir + FTC/TAF in Treatment-Naïve HIV-1–Positive Adults: Week 48 Results Study Design Primary Endpoint Week 0 48 96 144 B/F/TAF QD n=320 Treatment-Naïve Adults DTG + F/TAF Placebo QD HIV-1 RNA ≥500 copies/mL eGFRCG ≥30 mL/min 1:1 DTG + F/TAF QD n=325 B/F/TAF Placebo QD Phase 3, randomized, double-blind, active-controlled Study 1490 (ClinicalTrials.gov NCT02607956) Stratified by HIV-1 RNA, CD4 cell count, and geographic region (USA vs ex-USA) North America, Europe, Australia, and Latin America Chronic hepatitis B/C virus (HBV/HCV) infection allowed Primary endpoint: proportion with HIV-1 RNA <50 copies/mL at Week 48 Noninferiority margin of 12% based on US Food and Drug Administration-defined snapshot algorithm Background Inclusion criteria includes Antiretroviral treatment naïve (≤ 10 days of prior therapy with any antiretroviral agent following a diagnosis of HIV-1 infection) except the use for PrEP (pre-exposure prophylaxis) or PEP (post-exposure prophylaxis), up to one month prior to screening Screening genotype report must show sensitivity to FTC and TFV. Screening IN genosure was not performed. Exclusion criteria did not include HBV or HCV coinfection, except acute hepatitis in the 30 days prior to study entry eGFRCG, estimated glomerular filtration rate by Cockcroft-Gault equation.

Virologic Outcome at Week 48 Snapshot Analysis % Treatment Difference (95% CI) >99 1° B/F/TAF DTG + F/TAF PP Favors DTG + F/TAF Favors B/F/TAF -3.5 1° HIV-1 RNA <50 Copies/mL, % -7.9 1.0 -0.7 1.2 -2.6 PP HIV-1 RNA <50 Copies/mL HIV-1 RNA ≥50 Copies/mL No Virologic Data -12% 12% For modified snapshot: HIV-1 RNA > 50: BFTAF 91.4% (286/313) DTG+F/TAF 92·9% (302/325) difference-1·5% (−5.8% to 2.8%), p=0·48 HIV RNA >/=50: BFTAF 2.6% (8/313) DTG+FTAF 1.2% (4/325) Missing: BFTAF 6.1% (19/313) DTG+FTAF 5.8% (19/325) BFTAF 286 320 302 325 279 282 296 297 14 320 4 325 3 282 1 297 20 320 19 325 282 297 Primary endpoint of noninferiority met No resistance to any components of the treatment regimens occurred Sensitivity analyses confirmed noninferiority of B/F/TAF 1°, primary; CI, confidence interval; PP, per protocol.

Virologic Outcome at Week 48 Primary Endpoint Patients, n (%) B/F/TAF n=320 DTG + FTC/TAF n=325 HIV-1 RNA <50 copies/mL 286 (89.4) 302 (92.9) Difference for <50 copies/mL, % (95.002% CI) -3.5 (-7.9, 1.0; p=0.12) HIV-1 RNA ≥50 copies/mL 14 (4.4) 4 (1.2) 3 (0.9) 1 (0.3) D/C due to lack of efficacy D/C due to other reason* and last VL ≥50 copies/mL 11 (3.4) No virologic data in Week 48 window 20 (6.3) 19 (5.8) D/C due to AE/death D/C due to other reason* and last VL <50 copies/mL 14 (4.3) On study drug, but missing data in window 6 (1.9) 2 (0.6) This table describes the Snapshot outcome shown previously in greater detail. As you can see, there were a total of 4 subjects with VL ≥ 50 copies/mL in the Week 48 window, 3 on B/F/TAF and 1 on DTG + F/TAF. 1 B/F/TAF subject had a BL VL of 45,000. He was undetectable through Week 36, then was 1,690 copes/mL at Week 48 1 B/F/TAF subject had BL VL 25, 200 copies/mL. He was undetectable Weeks 4-36, then 15,400 copies at Week 48 1 B/F/TAF had a screening VL of 3.83 million copies/mL, which was 3.15 million on Day 1. He was never < 50 and had a VL of 315 copies/mL at Week 48. The 1 subject with HIV-1 RNA ≥ 50 at Week 48 on the DTG arm had a BL of 577,000 copies, and had 56 copies per mL at Week 48. This table also shows that a total of 14 subjects discontinued for a reason other than an AE or death but had HIV-1 RNA ≥ 50 copies at their last visit. Six of these subjects had their labs done, then took 1 dose of study medication on Day 1 and never returned for follow up. All 6 of these subjects were in the B/F/TAF arm, as shown in the next slide. In a post-hoc analysis which excluded only those 6 subjects+1 who dc’d due to AE/death (from no data category) and also did not provide postbaseline HIV RNA, the difference in response rates was 91.4% on B/F/TAF vs 92.9% for DTG + F/TAF. *Other reasons included investigator’s discretion, patient decision, lost to follow-up, noncompliance with study drug, protocol violation, and pregnancy. VL, viral load.

Reason for Discontinuation Patients Discontinued for Reasons Other Than Adverse Event/Death and Last HIV-1 RNA ≥50 Copies/mL Group Patient Day of Last HIV-1 RNA Last HIV-1 RNA, Copies/mL Reason for Discontinuation B/F/TAF 1 1 (baseline) 438* Patient decision (did not want to participate in study) 2 185,000* Protocol violation (incarcerated) 3 56,500* Lost to follow-up (moved away) 4 71,900* Investigator discretion (inconsistent state of residency) 5 17,300* Patient decision (no reason provided) 6 9600* Patient decision (moved away) 7 58 317,000 Investigator discretion (erratic behavior) 8 62 9000 Lost to follow-up (unresponsive to contact attempts) 9 169 23,400 Patient decision (wanted drug holiday) 10 176 4440 Investigator discretion (multiple missed appointments) 11 253 8630 DTG + F/TAF 12 213 Pregnancy 13 22,800 Lost to follow-up (incarcerated) 14 12,000 Noncompliance with study drug *Pretreatment baseline result

Further Results and Conclusions B/F/TAF was safe and well tolerated Treatment discontinuations due to adverse events were rare in both arms Lipid changes did not differ significantly between study arms Less decrease in eGFRCG was observed with B/F/TAF vs DTG + F/TAF No treatment discontinuations due to renal adverse events Further details of results in poster TUPDB0201LB Conclusions: Virologic suppression at Week 48 was high in both arms, and B/F/TAF was noninferior to DTG + F/TAF in treatment-naïve adults No patient discontinued due to lack of efficacy No treatment-emergent resistance to any study medication was observed These data reinforce the non-inferiority of B/F/TAF vs. DTG-based regimens seen in Study 1489 (abstract MOAB0105LB), presented yesterday