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GSK's Q1'26 Earnings Call: bepirovirsen in HBV, ADC pipeline in focus

Edited by Robert McTiernan··6 min read

GSK's Q1 2026 earnings conference call, held April 29, 2026, centered on three converging pipeline signals: positive Phase III data for bepirovirsen in chronic hepatitis B, an accelerating antibody-drug conjugate (ADC) build-out across gynecological and thoracic oncology, and a firm regulatory floor on the timeline for ViiV Healthcare's twice-yearly long-acting injectable HIV program.

Bepirovirsen at front of GSK's late-stage queue

Executives addressed the recent announcement of positive headline Phase III results for bepirovirsen, GSK's investigational functional cure for chronic hepatitis B (CHB). The B-Well 1 and B-Well 2 studies met their primary endpoints, with Chief Scientific Officer Tony Wood describing a statistically significant and clinically meaningful increase in functional cure rates without providing any further data specifics. Full data are scheduled for presentation at the European Association for the Study of the Liver (EASL) congress in May 2026.

The regulatory position for bepirovirsen has strengthened materially. The US FDA has granted Breakthrough Therapy Designation, with a PDUFA date set for October 26, 2026. China's National Medical Products Administration has accepted the filing for priority review. Wood noted that the US and China together represent approximately two-thirds of the global commercial opportunity for the asset.

Analysts pressed management on the likely label scope ahead of the EASL data. Wood declined to specify the expected label, but clarified that the B-Well 1 and 2 studies enrolled patients with surface antigen levels of 3,000 IU/mL or below, a population representing approximately 65% of the intent-to-treat population. The subgroup with surface antigen below 1,000 IU/mL — approximately 45% of the enrolled population — showed higher functional cure rates, and Wood acknowledged a relationship between surface antigen level and outcome, while cautioning against interpreting it as linear.

ADC oncology strategy accelerates on two fronts

GSK executives confirmed a deliberate and large-scale commitment to ADCs as a central oncology modality, with two assets advancing simultaneously into pivotal development.

Mo-Rez, GSK's B7-H4-targeting ADC developed in partnership with Hansoh Pharma, generated Phase I data from the global BEHOLD-1 study in advanced endometrial cancer (EC) and platinum-resistant ovarian cancer (PROC). At the highest doses evaluated, confirmed objective response rates reached 62% in PROC and 67% in advanced EC, with responses observed regardless of B7-H4 expression level. In the highest-dose PROC cohort, only one of 21 patients progressed within six months. Discontinuation rates were low, and pneumonitis — a class concern for ADCs — was reported in approximately 3% of patients at mild to moderate severity. Wood described the tolerability profile as differentiated.

GSK said it has now initiated two Phase III studies for Mo-Rez and plans to start three additional pivotal trials before the end of 2026, targeting EC and ovarian cancer populations. The pace of Phase III initiation — five pivotal trials within a single calendar year — is notable given that BEHOLD-1 Phase I data were only presented at the Society of Gynecological Oncology (SGO) meeting in April 2026.

Ris-Rez, GSK's B7-H3-targeting ADC, is advancing in parallel. The pivotal EMBOLD-301 study in second-line small cell lung cancer (SCLC) is recruiting. At the American Association for Cancer Research (AACR) annual meeting in April 2026, Hansoh presented data from the ARTEMIS-101 Phase I study evaluating Ris-Rez combined with a PD-L1 inhibitor in 40 patients with second-line-plus non-squamous non-small cell lung cancer (NSCLC). The combination produced a 47% objective response rate and a median progression-free survival of 14 months, with Grade 3 adverse events predominantly hematological and four cases of treatment-related interstitial lung disease, all Grade 1 or 2. GSK said these data supported the initiation of a Phase III NSCLC trial in China and plans to start a Phase II study combining Ris-Rez with Jemperli (dostarlimab) in a global population.

Wood also noted that Phase III trials for Ris-Rez in genitourinary cancers are scheduled to begin later in 2026, expanding the program beyond its initial SCLC focus.

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HIV pipeline timeline under scrutiny

Analysts used the GSK earnings transcript to press ViiV Healthcare CEO Deborah Waterhouse on whether the twice-yearly long-acting injectable HIV treatment program could be accelerated. Waterhouse confirmed that the FDA requires completion of Phase II development before Phase III can begin, and that this applies to all sponsors — eliminating any possibility of a regulatory shortcut.

The development sequence Waterhouse outlined is as follows: Phase IIA for VH184, a third-generation integrase strand transfer inhibitor (INSTI) with intellectual property protection through 2040, is already underway. Phase II for VH499, a capsid inhibitor, is expected to begin in the second half of 2026. Phase III initiation is targeted for 2028, with regulatory dialogue on trial design already underway. Waterhouse stated that this sequence supports an end-of-2030 approval for a twice-yearly long-acting injectable treatment regimen.

At the Conference on Retroviruses and Opportunistic Infections (CROI), ViiV presented data for VH184 showing potential for twice-yearly dosing and an enhanced in vitro resistance profile compared to bictegravir. VH499 also showed potential for twice-yearly dosing with a low risk of drug-drug interactions. Lotivibart, a broadly neutralizing antibody (bNAb), showed high efficacy for three-times-yearly dosing in combination with monthly cabotegravir, with twice-yearly data expected later in 2026.

Waterhouse also addressed the competitive threat from a once-weekly oral HIV regimen combining islatravir and lenacapavir, expected to launch in late 2026 or 2027. She argued that the long-acting injectable segment serves a distinct patient population — those with adherence challenges, stigma concerns, or a preference for directly observed therapy — and that weekly oral options are more likely to displace daily oral regimens than long-acting injectables.

Forward-looking catalysts

The second half of 2026 carries multiple Phase III readouts from the GSK pipeline. Jemperli will report pivotal results from the AZUR-1 study in rectal cancer, alongside data from a chemo-free endometrial cancer study. Camlipixant, a selective P2X3 receptor antagonist, will report CALM-2 Phase III results in refractory chronic cough — a readout Wood confirmed is on track following last patient, last visit completion, with publication expected around mid-year. Exdensur (depemokimab) will report Phase III data in eosinophilic granulomatosis with polyangiitis (EGPA), and ViiV's three-times-yearly cabotegravir pre-exposure prophylaxis registrational study data are also expected in the second half of 2026, with a launch targeted for the first half of 2027.

GSK said it plans to provide a comprehensive pipeline update at its Q2 2026 results in July, incorporating HIV pipeline details that had previously been scheduled for a standalone HIV-focused event. Chief Executive Luke Miels described the Q2 update as an opportunity to present the full portfolio in aggregate and explain the rationale behind the acceleration of late-stage assets.

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