REG - GSK PLC - GSK presents positive data for BEHOLD 1 B7 H4 ADC

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RNS Number : 0702A  GSK PLC  13 April 2026

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GSK presents positive data for B7-H4-targeted ADC in gynaecological cancers

·   Mocertatug rezetecan achieved confirmed objective response rates of 62%
in platinum-resistant ovarian cancer (PROC) and 67% in recurrent or advanced
endometrial cancer (EC) in BEHOLD-1 study

·   Current treatment options are limited for patients with PROC and EC

·   Promising efficacy and safety profile supports start of five pivotal
phase III trials in 2026

 

 

GSK plc (LSE/NYSE: GSK) today announced positive findings from its global
phase 1 BEHOLD-1 clinical trial for mocertatug rezetecan (or Mo-Rez for
short), a novel antibody-drug conjugate (ADC) targeting the B7-H4 antigen. At
the highest doses evaluated, Mo-Rez monotherapy achieved confirmed objective
response rates (cORR) of 62% (5.8 mg/kg n=21/34; 95% CI: 44, 78) in
platinum-resistant ovarian cancer (PROC) and 67% (4.8 mg/kg n=8/12; 95% CI:
35, 90) in recurrent or advanced endometrial cancer (EC). 1  (#_edn1) These
data will be presented for the first time in a late-breaking oral session at
the Society of Gynecologic Oncology (SGO) Annual Meeting on Women's Cancer in
San Juan, Puerto Rico.

 

Currently, there are limited treatment options with modest response rates for
patients with PROC and advanced EC. B7-H4 is an immune checkpoint that is
widely expressed in ovarian and endometrial cancers and is low in normal
tissues, providing potential for a differentiated precision-therapy. The
response to Mo-Rez observed across a range of B7-H4 expression levels
reinforces its broad potential in gynaecologic cancers and further validates
the relevance of targeting B7-H4.

 

Hesham Abdullah, Senior Vice President, Global Head Oncology, R&D, GSK,
said: "Treatment of gynaecological cancers remains a major challenge, with a
pressing need for new therapies that offer improved response rates. With
Mo-Rez, we now have compelling evidence of a promising clinical profile, with
response rates that support accelerating development into five pivotal global
phase III trials later this year across ovarian and endometrial cancers,
including earlier‑line settings."

 

Ana Oaknin, Study Investigator for BEHOLD-1, Medical Oncology Department,
Hospital Universitario Puerta de Hierro-Majadahonda, Madrid, Spain said: "In
the early phase BEHOLD-1 study, we saw meaningful antitumour activity for this
patient dataset, with response rates higher than typically seen in ADCs in
development, and a manageable safety profile. For patients with
platinum-resistant ovarian cancer and recurrent endometrial cancer, these
findings are particularly encouraging."

 

At the highest doses evaluated in BEHOLD-1, few patients needed to stop
treatment because of a treatment-related adverse events (TRAE) (0% in PROC and
4% in EC). The most common TRAE was nausea (82% in PROC; 75% in EC). Grade
≥3 TRAEs occurred in 64% and 54% patients in PROC and EC, respectively, and
were predominantly haematologic, as expected for treatments in this class.
Overall rates of interstitial lung disease or pneumonitis were low (3%; 5 out
of 178 patients) and all cases were mild to moderate (grade 1-2). The interim
analysis showed the median duration of response had not yet been reached.
Based on the findings from this study, the recommended dose for the first of
the phase III trials, BEHOLD-Ovarian01 and BEHOLD-Endometrial01, is 5.8 mg/kg.

 

About the BEHOLD clinical trial programme

The BEHOLD clinical programme is GSK's global development plan that includes
the BEHOLD-1 (NCT06431594) monotherapy study and the ongoing BEHOLD-2
(NCT06796907) combination study. Mo-Rez will advance to five pivotal global
phase III trials in 2026, starting with PROC (BEHOLD-Ovarian01 / NCT07286266)
and 2L EC (BEHOLD-Endometrial01 / NCT07286331). Additional phase III studies
will evaluate Mo‑Rez in platinum‑sensitive ovarian cancer
(BEHOLD-Ovarian02) and in first‑line maintenance settings for ovarian cancer
without homologous recombination deficiency (BEHOLD-Ovarian03) and
mismatch‑repair-proficient endometrial cancer (BEHOLD-Endometrial02).

 

About BEHOLD-1

The BEHOLD-1 clinical trial is a two-part, open-label, phase 1 study
evaluating the safety, tolerability and efficacy of Mo-Rez injection in
patients with PROC or advanced/recurrent EC. Phase 1a assessed up to four
Mo-Rez dose levels in patients with advanced solid tumours, with intravenous
administration every three weeks until progression or toxicity. In the phase
1b dose expansion, patients with PROC or EC (1-3 prior lines of therapy) were
randomised to three or two Mo-Rez dose levels, respectively.

 

At data cut-off, a total of 224 patients were enrolled in BEHOLD-1; n=44 in
phase 1a (n=21 PROC, n=23 mix of other solid tumours) and n=180 in phase Ib
(n=131 PROC, n=49 EC). Primary endpoints included: incidence of dose-limiting
toxicity in phase 1a and confirmed ORR (cORR) by investigator per RECIST 1.1
in phase Ib. At the highest dose evaluated in phase Ib, the most common
adverse events in PROC were nausea (86%), neutropenia/neutrophil count
decreased (73%), anaemia (52%), fatigue (52%) and alopecia (52%). In EC, the
most common adverse events were nausea (79%), neutropenia/neutrophil count
decreased (58%), anaemia (54%), vomiting (46%) and fatigue (42%).
Treatment‑related adverse events led to dose interruptions in 39% of
patients with PROC and 21% of those with EC, and to dose reductions in 39% in
PROC and 17% in EC, at the highest dose. The trial is ongoing and currently in
the dose expansion phase.

 

About mocertatug rezetecan

Mo-Rez is a novel investigational B7-H4-targeted antibody-drug conjugate
designed to optimise efficacy and tolerability. It is composed of a fully
human anti-B7-H4 monoclonal antibody covalently linked to a topoisomerase
inhibitor payload and has a drug-to-antibody ratio (DAR) of 6. GSK acquired
exclusive worldwide rights (excluding China's mainland, Hong Kong, Macau, and
Taiwan) from Hansoh Pharma to progress clinical development and
commercialisation of Mo-Rez globally.

 

About ovarian cancer and endometrial cancer

Endometrial cancer affects 1.6 million people globally, with 417,000 new cases each year and 15% to 20% of patients presenting in later stages of the disease.
 2  (#_edn2)
(,
 3  (#_edn3)
) Ovarian cancer affects 843,000 people with 240,000 new cases annually.
 4  (#_edn4)
 70% of these patients present with advanced disease.
 5  (#_edn5)
 Recurrence is common in advanced cases of disease, up to 67% in endometrial cancer and 70% in ovarian cancer, and survival usually declines after recurrence.
 6  (#_edn6)
(,
 7  (#_edn7)
)

GSK in oncology

Our ambition in oncology is to help increase overall quality of life, maximise
survival and change the course of disease, expanding from our current focus on
blood and women's cancers into lung and gastrointestinal cancers, as well as
other solid tumours. This includes accelerating priority programmes such as
antibody-drug conjugates targeting B7-H3 and B7-H4, and IDRX-42, a highly
selective KIT tyrosine kinase inhibitor.

About GSK

GSK is a global biopharma company with a purpose to unite science, technology,
and talent to get ahead of disease together. Find out more at www.gsk.com
(https://www.gsk.com) .

 

 

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Cautionary statement regarding forward-looking statements

GSK cautions investors that any forward-looking statements or projections made
by GSK, including those made in this announcement, are subject to risks and
uncertainties that may cause actual results to differ materially from those
projected. Such factors include, but are not limited to, those described in
the "Risk Factors" section in GSK's Annual Report on Form 20-F for 2025.

 

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References

 1  (#_ednref1) Oaknin A, McKean W, van Dongen M et al. Mocertatug Rezetecan
(GSK5733584), a B7-H4 Targeted Antibody Drug Conjugate, in Platinum-Resistant
Ovarian Cancer and Endometrial Cancer: First Results from the Global BEHOLD-1
Study. Presented at the Society of Gynecologic Oncology (SGO) Annual Meeting
on Women's Cancer 2026. April 2026.

 2  (#_ednref2) Sung H, Ferlay J, Siegel R, et al. Global Cancer Statistics
2020: GLOBOCAN Estimates of Incidence and Mortality Worldwide for 36 Cancers
in 185 Countries. CA Cancer J Clin. 2021;71(3):209-249.
doi:10.3322/caac.21660.

 3  (#_ednref3) CMP: CancerMPact® Patient Metrics Mar-2023, Cerner Enviza.

 4  (#_ednref4) Ren Y, Xu R, Wang Y, Su L, Su J. Global, regional, and
national burden of ovarian cancer in women aged 45 + from 1990 to 2021 and
projections for 2050: a systematic analysis based on the 2021 global burden of
disease study. J Cancer Res Clin Oncol. 151(8):225.
doi:10.1007/s00432-025-06277-9.

 5  (#_ednref5) Rauh-Hain JA, Krivak TC, Del Carmen MG et al. Ovarian cancer
screening and early detection in the general population. Rev Obstet Gynecol.
2011;4(1):15-21.

 6  (#_ednref6) Shelvin KB, Vincent J, Morron S, Morin M, Mammoser A, Nair N.
Recurrent high grade serous endometrial cancer with brain metastases:
Immunotherapy confers improved quality of life and survival. Gynecol Oncol
Rep. 2024;55:101494. doi:10.1016/j.gore.2024.101494.

 7  (#_ednref7) Salas Bolívar P, Gonzalez-Benitez C, Carbonell López M,
Díez Sebastian J, Hernández Gutiérrez A, Zapardiel I. Prognostic Factors
After the First Recurrence of Ovarian Cancer. Journal of Clinical Medicine.
2025; 14(2):470. https://doi.org/10.3390/jcm14020470.

 

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