Gilead Sciences, Inc. (GILD Quick QuoteGILD - Free Report) and partner Merck (MRK Quick QuoteMRK - Free Report) announced positive data from two late-stage studies, ISLEND-1 and ISLEND-2, evaluating investigational oral once-weekly single-tablet HIV treatment regimen of islatravir/lenacapavir.

The investigational regimen combines Merck's islatravir, a next-generation nucleoside analog that inhibits HIV replication through multiple mechanisms, including reverse transcriptase translocation inhibition, with Gilead's lenacapavir, a first-in-class capsid inhibitor designed to disrupt the virus at several stages of its lifecycle.

Both studies met the primary efficacy endpoint at week 48.

Gilead’s shares have gained 2.2% year to date against the industry's decline of 3.1%.

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More on GILD and MRK’s HIV Studies

The ISLEND studies are evaluating the efficacy and safety of islatravir 2 mg/lenacapavir 300 mg (ISL/LEN) in people with HIV who are virologically suppressed and switched from Biktarvy (bictegravir 50 mg/emtricitabine 200 mg/tenofovir alafenamide 25 mg tablets, B/F/TAF) (ISLEND-1) or standard of care antiretroviral regimens (ISLEND-2).

The primary efficacy endpoint in both ISLEND-1 and ISLEND-2 was the proportion of participants with HIV-1 RNA levels ≥ 50 copies/mL at week 48, as measured by the FDA snapshot algorithm. In ISLEND-1, a double-blind study, the once-weekly oral regimen of islatravir/lenacapavir (ISL/LEN) demonstrated non-inferior efficacy compared with Biktarvy. Similarly, in the open-label ISLEND-2 trial, ISL/LEN achieved non-inferior results versus standard daily oral antiretroviral therapies.

The regimen also showed a safety profile comparable to the respective comparator treatments in both studies, with no new safety concerns identified.

Following the positive phase III results, Gilead and Merck intend to submit the ISLEND trial data to regulatory authorities worldwide and present detailed study findings at an upcoming scientific conference.

The investigational once-weekly oral combination of islatravir and lenacapavir could become the first long-acting oral HIV treatment with weekly dosing, potentially offering people living with HIV a new and more convenient treatment option if approved.

Gilead is a dominant player in the HIV market.

Gilead’s Biktarvy is a once-daily, single-tablet HIV treatment that combines three antiretroviral medicines, including bictegravir, a potent integrase strand transfer inhibitor (INSTI) with the Descovy backbone of emtricitabine and tenofovir alafenamide. The regimen offers convenient dosing with or without food, has a low potential for drug interactions, and provides a high barrier to resistance.

In 2025, the FDA approved lenacapavir for the prevention of HIV under the brand name Yeztugo for pre-exposure prophylaxis to reduce the risk of sexually acquired HIV in adults and adolescents weighing at least 35 kg.

The approval has significantly boosted Gilead’s HIV franchise, as lenacapavir needs to be taken twice yearly, unlike daily oral pills.  

Following Yeztugo’s strong first-quarter performance and improving market trends, Gilead raised its 2026 sales guidance to $1 billion, positioning the drug to achieve blockbuster status in its first full year on the market.

Approval of additional better treatments should bolster GILD’s HIV franchise in the wake of increasing competition from the likes of GSK plc (GSK Quick QuoteGSK - Free Report) .

GSK continues to grow its HIV business, driven by strong patient demand for long-acting injectable medicines (Cabenuva and Apretude) and Dovato.

GILD, MRK Update on Lung Cancer Study

Concurrently, Merck and Gilead Sciences announced the discontinuation of the phase III KEYNOTE-D46/EVOKE-03 study evaluating Trodelvy (sacituzumab govitecan-hziy) in combination with Keytruda as a first-line treatment for patients with metastatic non-small cell lung cancer (NSCLC) whose tumors express high levels of PD-L1 (TPS ≥50%).

The open-label phase III study sponsored by Merck evaluated Trodelvy in combination with Keytruda versus Keytruda alone in this NSCLC patient population. The trial enrolled approximately 620 patients.

The decision follows a recommendation from the external Data Monitoring Committee after reviewing the pre-specified final progression-free survival (PFS) analysis and an interim overall survival (OS) analysis. While the combination demonstrated a numerical improvement in PFS compared with Keytruda alone, the result did not achieve statistical significance. Additionally, the committee concluded that the likelihood of demonstrating a statistically significant OS benefit at the final analysis was low.

The companies plan to present the detailed study results at a future medical conference.

Gilead’s Trodelvy is a first-in-class Trop-2-directed antibody-drug conjugate.

Trodelvy is currently approved in various countries for patients with metastatic triple-negative breast cancer who have received at least one prior therapy and for certain patients with previously treated HR-positive/HER2-negative metastatic breast cancer. 
Trodelvy continues to gain market share in the second-line setting. GILD has submitted two supplemental biologics license applications seeking approval of the drug for use in first-line metastatic triple-negative breast cancer patients.

MRK’s blockbuster immuno-oncology drug Keytruda is approved for several types of cancer and alone accounts for around 50% of sales.

GILD’s Zacks Rank

Gilead currently has a Zacks Rank #3 (Hold). You can see the complete list of today’s Zacks #1 Rank (Strong Buy) stocks here.