LONDON (dpa-AFX) - GSK plc (GSK, GSK.L) announced encouraging findings from its global phase I BEHOLD-1 clinical trial for mocertatug rezetecan (Mo-Rez), a novel antibody-drug conjugate (ADC) targeting the B7-H4 antigen. At the highest doses evaluated, Mo-Rez monotherapy achieved confirmed objective response rates of 62% in platinum-resistant ovarian cancer (PROC) and 67% in recurrent or advanced endometrial cancer (EC).
Currently, treatment options for patients with PROC and advanced EC are limited, with modest response rates. B7-H4, an immune checkpoint widely expressed in ovarian and endometrial cancers but low in normal tissues, offers potential for a differentiated precision therapy. The responses observed across varying levels of B7-H4 expression highlight Mo-Rez's broad potential in gynecologic cancers and reinforce the relevance of targeting this antigen.
At the highest doses in BEHOLD-1, few patients discontinued treatment due to 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% of PROC patients and 54% of EC patients, primarily hematologic in nature, consistent with expectations for this class of therapy. Rates of interstitial lung disease or pneumonitis were low, with all cases mild to moderate. The interim analysis showed that the median duration of response had not yet been reached. Based on these findings, the recommended dose for the first phase III trials-BEHOLD-Ovarian01 and BEHOLD-Endometrial01-is 5.8 mg/kg.
The company stated that the promising efficacy and safety profile supports the launch of five pivotal phase III trials in 2026.
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GSK closed at $58.21, marking a decline of $0.15 or 0.26%. In overnight trading at 8:41:46 PM EDT, the stock edged up slightly to $58.29, an increase of $0.08 or 0.14%.
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