Merck’s sacituzumab tirumotecan meets both primary endpoints in the pivotal Phase 3 TroFuse-005 trial for advanced endometrial cancer, Relay Therapeutics reports the first clinical evidence of PI3Kα mutant-selective inhibition in PIK3CA-driven vascular anomalies in its Phase 2 ReInspire trial, Regeneron’s fianlimab combination narrowly misses statistical significance in its Phase 3 melanoma trial, and Sanofi’s efdoralprin alfa demonstrates superiority over standard-of-care augmentation therapy in a Phase 2 study of alpha-1 antitrypsin deficiency-related emphysema, the most significant clinical trial results 22 May 2026 has to offer from across the pipeline.
This week delivered consequential readouts spanning oncology, rare vascular disease, and rare respiratory disease, reflecting the broadening reach of precision medicine across both common and underserved conditions. The antibody-drug conjugate result stands as one of the more consequential Phase 3 results in women’s cancers so far in 2026, demonstrating for the first time that a TROP2-directed ADC can improve both overall and progression-free survival over chemotherapy in a post-immunotherapy setting. Alongside that, proof-of-concept data in a rare genetic vascular disorder and a potential step-change in augmentation therapy for a chronic lung disease each illustrate the pipeline’s growing ambition to move beyond symptomatic management. Here, Life Science Daily News brings you the most significant clinical trial results 22 May 2026.
Merck’s Sacituzumab Tirumotecan Meets Phase 3 Primary Endpoints in Advanced Endometrial Cancer
Merck announced on 18 May 2026 that the pivotal Phase 3 TroFuse-005 trial evaluating sacituzumab tirumotecan (sac-TMT), an investigational TROP2-directed antibody-drug conjugate (ADC) developed in collaboration with Kelun-Biotech, met its primary endpoints of overall survival (OS) and progression-free survival (PFS) in patients with advanced or recurrent endometrial cancer. TroFuse-005 is the first global Phase 3 trial to demonstrate statistically significant improvement in both OS and PFS compared to chemotherapy in this patient population, and sac-TMT is the first and only ADC to achieve this outcome in endometrial cancer.
TroFuse-005 was a randomised, active-controlled, open-label, multicentre, global Phase 3 trial enrolling 776 patients with advanced or recurrent endometrial cancer whose disease had progressed following prior platinum-based chemotherapy and anti-PD-1/L1 immunotherapy. Patients were randomised to receive either sac-TMT or physician’s choice chemotherapy, comprising doxorubicin or paclitaxel. At a pre-specified interim analysis, sac-TMT demonstrated statistically significant improvements in both primary endpoints compared with chemotherapy. The key secondary endpoint of objective response rate was also met. The safety profile was consistent with prior studies of the drug, with no new safety signals identified.
Sac-TMT is a TROP2-directed ADC that combines a targeting antibody with a potent cytotoxic payload, exploiting the overexpression of TROP2 on tumour cells relative to healthy tissue to deliver selective cancer cell killing. Endometrial cancer is estimated to affect approximately 68,270 patients in the United States in 2026, with around 14,450 deaths expected from the disease. Patients who progress after platinum-based chemotherapy and checkpoint immunotherapy represent a population with limited effective options. TroFuse-005 represents the first positive Phase 3 result from Merck’s broader TroFuse clinical development programme, which encompasses 17 ongoing global Phase 3 trials across multiple tumour types, including ten focused on women’s cancers. Merck has stated it plans to present the full trial data at an upcoming medical meeting and to discuss the results with regulatory authorities worldwide.
Relay Therapeutics’ Zovegalisib Reports First Clinical Evidence of PI3Kα-Selective Inhibition in PIK3CA-Driven Vascular Anomalies
Relay Therapeutics announced on 19 May 2026 initial clinical data from the Phase 2 ReInspire trial evaluating zovegalisib, an investigational oral PI3Kα mutant-selective inhibitor, in patients with PIK3CA-driven vascular anomalies. The data, presented at the International Society for the Study of Vascular Anomalies (ISSVA) World Congress 2026 in Philadelphia, represent the first clinical demonstration of the potential benefits of PI3Kα mutant-selective inhibition in this rare disease setting.
As of the 15 April 2026 data cut-off, 32 patients aged 12 and above were enrolled and randomised across three dose cohorts in the Part 1 dose selection portion of the study. Of the 20 patients who had reached the 12-week response evaluation timepoint, 60% achieved a confirmed volumetric response, defined as a reduction in target lesion volume of 20% or greater by blinded independent central review. A further 95% of enrolled patients experienced some degree of lesion volume reduction. Investigator-reported clinical improvement was observed in 89% of patients and patient-reported clinical improvement in 79% at week 12. All 32 patients remained on treatment as of the data cut-off date, and no patients discontinued due to adverse events. Among the 22 patients treated at the two lower dose levels of 100 mg and 300 mg twice daily, dose reductions were seen in 23% of patients and only 9% experienced a Grade 3 or higher treatment-related adverse event. The 400 mg twice-daily dose showed a less favourable tolerability profile and has been deprioritised; the 400 mg once-daily and 300 mg twice-daily doses have been selected for expansion cohorts, with enrolment ongoing.
Vascular anomalies are a group of rare, often debilitating disorders caused by abnormal development of blood vessels and lymphatic vessels, frequently driven by activating PIK3CA mutations. Conditions within this spectrum, including PIK3CA-related overgrowth spectrum, lymphatic malformations, and venous malformations, can cause chronic pain, swelling, disfigurement, and impaired mobility, and are estimated to affect approximately 170,000 patients in the United States. Current systemic treatment options are limited and may be associated with tolerability challenges that restrict long-term use. Zovegalisib is designed to inhibit specifically the mutant form of PI3Kα, seeking to avoid the systemic toxicities associated with broader PI3K inhibition. The company is continuing enrolment of expansion cohorts for adults and adolescents and a paediatric dose-finding cohort for children aged six to eleven, while also advancing a Phase 3 programme in PI3Kα-mutated hormone receptor-positive, HER2-negative advanced breast cancer.
Regeneron’s Fianlimab Combination Narrowly Misses Primary Endpoint in Phase 3 First-Line Melanoma Trial
Regeneron announced on 15 May 2026 results from the Phase 3 trial evaluating two dose levels of fianlimab, a LAG-3 inhibitor, in combination with cemiplimab (PD-1 inhibitor) as a first-line treatment for patients with unresectable locally advanced or metastatic melanoma. The trial did not reach statistical significance for the primary endpoint of improvement in progression-free survival (PFS) compared to pembrolizumab monotherapy. No new safety signals were identified with the fianlimab combination.
The high-dose fianlimab combination achieved a median PFS of 11.5 months compared with 6.4 months for pembrolizumab, a numeric improvement of 5.1 months corresponding to a hazard ratio of 0.845 (95% CI: 0.709, 1.008; p=0.0627), which narrowly missed the threshold for statistical significance. The low-dose combination also failed to meet the primary endpoint (HR 0.931; p=0.4661). Detailed results from the trial will be presented at an upcoming medical meeting. A separate head-to-head Phase 3 trial of the high-dose fianlimab combination versus Opdualag (nivolumab and relatlimab) is ongoing and continues to enrol.
Fianlimab is being developed as part of Regeneron’s broader immuno-oncology strategy aimed at combining LAG-3 checkpoint inhibition with PD-1 blockade to achieve deeper and more durable anti-tumour responses. LAG-3 is an inhibitory receptor on T cells that, when blocked alongside PD-1, can enhance immune cell activation against tumours. Melanoma is one of the most immunotherapy-responsive tumour types, and the competitive first-line landscape is defined by pembrolizumab monotherapy and the approved dual checkpoint combination of nivolumab plus relatlimab. The failure to reach the primary endpoint represents a setback for fianlimab’s melanoma programme, though the company retains a developmental pathway through the ongoing head-to-head comparison against Opdualag.
Sanofi’s Efdoralprin Alfa Demonstrates Superiority Over Standard of Care in Phase 2 Alpha-1 Antitrypsin Deficiency Trial
Sanofi presented data on 18 May 2026 from the global Phase 2 ElevAATe study at the 2026 American Thoracic Society International Conference in Orlando. The data demonstrated superiority of investigational efdoralprin alfa over standard-of-care plasma-derived alpha-1 antitrypsin (AAT) augmentation therapy in achieving and maintaining normalised functional AAT (fAAT) levels in adults with alpha-1 antitrypsin deficiency (AATD)-related emphysema.
Efdoralprin alfa, dosed every three weeks, achieved mean increases in fAAT trough levels more than three times greater than those produced by weekly plasma-derived protein therapy, meeting the primary endpoint (p<0.0001). All key secondary endpoints were also met (p<0.0001). In the group receiving the investigational therapy every three weeks, fAAT levels remained above the normal protective threshold of 23.8 μM for 100% of days during the 32-week study, compared with 41% of days for those on standard augmentation therapy. The safety profile was consistent with prior experience, with no new safety signals identified. Sanofi has also noted that data support both three-week and four-week dosing regimens for efdoralprin alfa, a potentially meaningful improvement in convenience compared to the current weekly intravenous standard of care, which has remained essentially unchanged for approximately 40 years.
Alpha-1 antitrypsin deficiency is a rare, underdiagnosed genetic disorder caused by mutations in the SERPINA1 gene, resulting in deficient or dysfunctional AAT protein. Without adequate AAT, the lungs are vulnerable to unopposed protease-driven inflammation and progressive destruction, leading to emphysema. An estimated 90% of individuals with AATD are believed to be undiagnosed. Efdoralprin alfa is a recombinant fusion protein distinct from existing plasma-derived therapies, designed to restore and maintain normal AAT levels through less frequent dosing. If the clinical benefit of normalised fAAT levels translates into preserved lung function and reduced exacerbations in longer-term studies, efdoralprin alfa could represent the first meaningful advance in AATD augmentation therapy in four decades. Sanofi is expected to advance the programme into pivotal registrational development.
Looking Ahead
This week’s clinical trial results 22 May 2026 reflect a pipeline in which precision medicine and novel therapeutic modalities are challenging long-established standards of care across multiple disease areas. Merck’s ADC result in endometrial cancer signals that TROP2-directed therapy may substantially reshape treatment for patients who have progressed beyond immunotherapy, a population that has lacked effective options. Relay’s vascular anomalies data provide the first clinical proof of concept for targeting PIK3CA mutations in rare vascular disorders, opening a potential new pharmacological approach for patients who have historically relied on surgery and interventional procedures. The AATD readout illustrates that a therapy combining recombinant protein engineering with reduced dosing frequency could finally modernise a standard of care that has remained static for nearly four decades. Life Science Daily News will continue to bring you accurate, timely coverage of the clinical trial results 22 May 2026 that matter most across the global life sciences pipeline.
This clinical trials roundup is produced by the Life Science Daily News editorial team. All stories are selected and written independently.
