ASCO26: 5 data snapshots ahead of the year’s biggest cancer drug meeting

Merck's Sacituzumab Tirumotecan Shows Strong Phase 3 NSCLC Efficacy

Merck & Co. and Kelun Biotech's antibody-drug conjugate, sacituzumab tirumotecan (sac-TMT), demonstrated significant efficacy in a Phase 3 trial (OptiTROP-Lung05) for first-line non-small cell lung cancer (NSCLC) in China. When combined with Keytruda, sac-TMT reduced the risk of disease progression by 65% compared to Keytruda alone. The combination also achieved an impressive overall response rate of just over 70%, significantly higher than Keytruda's 42%, with comparable or lower discontinuation rates. These results, unveiled ahead of the ASCO annual meeting, are considered "optically very impressive" by analysts, bolstering Merck's strategy for sac-TMT as a "bio-better chemo."

• The Phase 3 OptiTROP-Lung05 trial showed that sacituzumab tirumotecan (sac-TMT) combined with Keytruda significantly reduced the risk of disease progression by 65% in first-line non-small cell lung cancer patients compared to Keytruda monotherapy. The combination also achieved an overall response rate exceeding 70%, substantially higher than the 42% observed with Keytruda alone, indicating robust anti-tumor activity.
• Analysts lauded the results as "optically very impressive," suggesting they de-risk Merck's global lung cancer trials for sac-TMT. Leerink Partners noted the data supports sac-TMT's positioning as a "bio-better chemo," potentially placing Merck on par with emerging bispecific antibodies for lung tumors and strengthening its competitive stance in the oncology market.
• While the data is strong, Stifel analysts cautioned against direct comparisons to other bispecific drugs like Akeso and Summit's ivonescimab due to trial design differences, suggesting no immediate threat to ivonescimab's competitive positioning. Nevertheless, the positive outcomes from OptiTROP-Lung05 provide a crucial proof point for sac-TMT's potential to become a major asset in Merck's future oncology portfolio.

OptiTROP-Lung05: Sacituzumab Tirumotecan's Impressive NSCLC Efficacy and Safety

The Phase III PAPILLON study (2025) evaluated amivantamab-chemotherapy combination versus chemotherapy alone in 308 participants with EGFR exon 20 insertion-mutated NSCLC. The study demonstrated remarkable efficacy outcomes, with median time to treatment discontinuation extending to 13.2 months versus 7.5 months for chemotherapy alone (HR 0.38, 95% CI 0.28-0.51; p<0.0001). Additionally, median time to subsequent therapy reached 17.7 months compared to 9.9 months (HR 0.35, 95% CI 0.25-0.49; p<0.0001), with crossover-adjusted overall survival showing hazard ratios of 0.52-0.60, more pronounced than the planned interim intention-to-treat analysis.

Recent pembrolizumab studies (2025) have provided important insights into PD-L1-negative advanced NSCLC treatment. A retrospective cohort study of 246 patients comparing pembrolizumab plus chemotherapy versus platinum-based dual chemotherapy showed significant progression-free survival improvement (9.5 versus 7.2 months; HR=0.64, 95% CI: 0.46-0.87; P=0.004). Particularly noteworthy outcomes were observed in squamous cell lung cancer patients, with PFS extending to 13.8 months versus 4.8 months in the control group (P<0.001). Safety analysis revealed grade ≥3 non-immune-related adverse events in 46.8% of pembrolizumab-treated patients versus 33.1% in the chemotherapy group, with immune-related adverse events occurring in 39.5% of patients, though no grade 5 events were reported.

The ALEX study (2025) final analysis provided long-term survival data for alectinib versus crizotinib in treatment-naïve advanced ALK-positive NSCLC. After a median follow-up of 53.5 months, alectinib demonstrated superior median overall survival of 81.1 months compared to 54.2 months for crizotinib (HR 0.78; 95% CI 0.56-1.08). The benefit was particularly pronounced in patients with CNS metastases, showing median overall survival of 63.4 months versus 30.9 months for crizotinib. The median duration of response was substantially longer with alectinib at 42.3 months compared to 11.1 months for crizotinib (HR 0.41; 95% CI 0.30-0.56), with no new or unexpected safety concerns identified during the extended follow-up period.

Sacituzumab Tirumotecan's Place Among Emerging NSCLC Combination Therapies

Recent clinical trials are evaluating diverse combination therapy approaches for NSCLC, spanning immunotherapy, targeted therapy, chemotherapy, and novel agent combinations. These investigations aim to overcome resistance mechanisms and improve outcomes through synergistic therapeutic strategies.

Expanding Horizons: Sacituzumab Tirumotecan's Broad Oncology Pipeline

Sacituzumab tirumotecan is being evaluated across multiple solid tumor types beyond NSCLC, with several trials demonstrating promising clinical activity. The development program encompasses both early-phase dose-finding studies and pivotal registration trials across different oncology indications.

• Triple-negative breast cancer (TNBC) - The OptiTROP-Breast01 phase 3 randomized controlled trial (NCT05347134) compared sacituzumab tirumotecan versus chemotherapy in patients with locally recurrent or metastatic TNBC who had received ≥2 prior therapies, demonstrating median PFS of 6.7 months versus 2.5 months (HR 0.32; P<0.00001) and ORR of 45.4% versus 12.0%

• HR+/HER2- breast cancer - Phase 2 expansion cohorts within the MK-2870-001/KL264-01 study evaluated sacituzumab tirumotecan at recommended doses, achieving an ORR of 31.7% (95% CI: 18.1%-48.1%) in 41 patients with hormone receptor-positive, HER2-negative breast cancer

• Advanced or metastatic urothelial carcinoma - Cohort 9 of the phase 1/2 study (NCT04152499) enrolled patients with disease progression on ≥1 prior platinum-based chemotherapy and anti-PD-(L)1 therapy, demonstrating confirmed ORR of 31% (95% CI: 18%-45%) and median PFS of 5.5 months with sacituzumab tirumotecan 5 mg/kg every 2 weeks

• Advanced solid tumors - The first-in-human MK-2870-001/KL264-01 study employed a phase 1 dose-escalation design (2-12 mg/kg every 2 weeks) in patients with unresectable locally advanced/metastatic solid tumors refractory to standard therapies, establishing MTD at 5.5 mg/kg and recommended expansion doses of 4-5 mg/kg

• Gynecologic cancers - Sacituzumab tirumotecan is being investigated as part of the broader ADC development pipeline for patients with recurrent gynecologic tumors, though specific trial design details were not detailed in available literature

Sac-TMT's First-Line NSCLC Data: Reshaping the Treatment Paradigm

The recent unveiling of Phase 3 data for sacituzumab tirumotecan (sac-TMT) in combination with Keytruda for first-line non-small cell lung cancer (NSCLC) marks a pivotal moment in oncology. Achieving a 65% reduction in disease progression risk and an overall response rate exceeding 70% compared to Keytruda alone is a compelling demonstration of efficacy, suggesting a significant leap forward for patients facing this aggressive disease. This performance reinforces the growing prominence of antibody-drug conjugates (ADCs) as a transformative class of therapeutics, particularly TROP2-directed agents like sac-TMT, which are increasingly seen as "bio-better chemo" options.

For Merck, these results validate a strategic bet on sac-TMT, positioning it as a cornerstone of their oncology portfolio beyond its established role in metastatic triple-negative breast cancer and later-line EGFR-mutant NSCLC. The success of this ADC-immunotherapy combination also signals a broader trend in cancer treatment, where synergistic approaches are unlocking unprecedented responses. This could accelerate the development of similar combination regimens, potentially redefining the standard of care in first-line NSCLC and influencing how future clinical trials are designed.

However, the path forward is not without its considerations. While ADCs offer targeted delivery of cytotoxic payloads, they are associated with distinct safety profiles. Myelosuppression, manifesting as hematologic toxicities, is a common concern across ADCs, including sac-TMT. Furthermore, interstitial lung disease (ILD) remains a notable adverse event for TROP2-directed ADCs, necessitating vigilant patient monitoring and proactive management strategies. The trial's focus on a Chinese population also raises questions about the direct generalizability of these results to other global patient cohorts, which may exhibit different genetic predispositions or treatment landscapes. Moreover, the TROP2 ADC space in NSCLC is rapidly becoming crowded, with several agents vying for market share. Differentiation based on efficacy, safety, and specific patient populations will be crucial. As the field progresses, optimizing patient selection, potentially through advanced biomarker identification, and refining combination strategies will be key to maximizing the therapeutic potential of these powerful new agents.