Sacituzumab Tirumotecan and Pembrolizumab: A New First-Line Treatment in Lung Cancer

A New First-Line Signal in PD-L1-Positive Advanced Lung Cancer: Sacituzumab Tirumotecan + Pembrolizumab Strongly Prolonged PFS

Adding an ADC to Immunotherapy: A New First-Line Rationale in Lung Cancer

Immunotherapy has fundamentally changed the treatment paradigm in advanced NSCLC, particularly in PD-L1-positive patients. While pembrolizumab monotherapy can provide long-lasting responses in patients with PD-L1 TPS ≥50, immunotherapy alone may not always provide sufficiently deep or prolonged disease control in the PD-L1 TPS 1–49 range. A frequent clinical question is therefore: should we add chemotherapy for these patients, give immunotherapy alone, or strengthen immunotherapy with a smarter and more targeted payload carrier?

OptiTROP-Lung05 offers a new answer to this question. Instead of conventional chemotherapy, sacituzumab tirumotecan, a TROP2-targeted ADC, is added to pembrolizumab. This is the idea of combining a cytotoxic payload targeting tumor cells with PD-1 blockade activating the immune system within the same treatment strategy.

A Phase 3 Study of 413 PD-L1-Positive, EGFR/ALK-Negative Patients

OptiTROP-Lung05 is a randomized, open-label, multicenter phase 3 study. It enrolled patients with stage IIIB/IIIC or stage IV NSCLC who had received no previous systemic antitumor therapy for locally advanced or metastatic disease, had PD-L1 TPS ≥1, no EGFR or ALK alterations, and an ECOG performance score of 0–1.

Patients were assigned to two arms in a 1:1 ratio. In the combination arm, sacituzumab tirumotecan 4 mg/kg was given every 2 weeks and pembrolizumab 400 mg every 6 weeks. In the control arm, pembrolizumab 400 mg was administered every 6 weeks as monotherapy. The primary endpoint was progression-free survival according to blinded independent central review.

A Very Strong Difference in PFS: HR 0,35

At the data cutoff of 29 September 2025, median follow-up was 10,5 months. According to BICR, median PFS had not yet been reached in the sacituzumab tirumotecan + pembrolizumab arm; in the pembrolizumab monotherapy arm it was 5,7 months . The hazard ratio was reported as 0,35 , meaning an approximately 65% relative reduction in the risk of progression or death. The P value was <0,0001 .

The Difference in PD-L1 Subgroups Is Particularly Striking in the TPS 1–49 Group

In the PD-L1 TPS ≥50 group, the HR favoring the combination was 0,47 . In the PD-L1 TPS 1–49 group, the HR was reported as 0,28 . This finding is clinically important because patients with TPS 1–49 are the group in which pembrolizumab alone is most debated. Adding an ADC in this group may fill the biological gap where immunotherapy monotherapy can prove insufficient.

Response Rate of 70,2%: More Frequent and Deeper Tumor Shrinkage

The objective response rate in the combination arm was %70,2, compared with %42,0 in the pembrolizumab monotherapy arm. The absolute difference was reported as approximately 28,3 percentage points . In addition, deep response, meaning at least 50% shrinkage in the sum of target lesion diameters, occurred in %49,0in the combination arm versus %25,9 in the pembrolizumab arm.

Overall Survival Is Not Yet Mature, but the Early Signal Favors the Combination

Overall survival data were not yet mature at the interim analysis and were assessed descriptively by the investigators. There were 33 deaths (15,9%) in the combination arm and 54 deaths (26,3%) in the pembrolizumab arm. Median OS had not yet been reached in the combination arm; it was reported as 14,5 months in the pembrolizumab arm. The HR was 0,55 . The 12-month OS rate was %80,4in the combination arm versus %68,9 in the pembrolizumab arm.

Efficacy Increases, and So Does the Burden of Adverse Effects

Sac-TMT + pembrolizumab provided greater efficacy, but the burden of adverse effects was higher than with pembrolizumab monotherapy. Grade 3 or higher treatment-emergent adverse events occurred in %55,3in the combination arm versus %31,4 in the pembrolizumab arm. Serious adverse event rates were reported as %38,9 and %28,9 , respectively.

The most frequently reported adverse effects in the combination arm were hematologic and mucosal toxicities: anemia, decreased neutrophils, decreased leukocytes, alopecia, and stomatitis were prominent. Ocular surface toxicity and infusion reactions were also among adverse effects of special interest for Sac-TMT.

From Pembrolizumab Monotherapy to the Era of ADC + Immunotherapy?

Pembrolizumab monotherapy became established in clinical practice for PD-L1-positive advanced NSCLC through studies such as KEYNOTE-024 and KEYNOTE-042. KEYNOTE-024 demonstrated the superiority of pembrolizumab monotherapy over chemotherapy in patients with PD-L1 TPS ≥50. KEYNOTE-042 opened the door to the PD-L1 TPS ≥1 patient group; however, the benefit is known to be stronger particularly in the TPS ≥50 group, with monotherapy decisions more controversial in the TPS 1–49 group.

Meanwhile, pembrolizumab + chemotherapy became standard in both nonsquamous and squamous advanced NSCLC through KEYNOTE-189 and KEYNOTE-407. Adding chemotherapy, however, means greater toxicity, hair loss, myelosuppression, and treatment burden. An ADC + immunotherapy strategy offers a new possibility in this equation: a tumor-targeted cytotoxic payload instead of conventional chemotherapy.

TROP2 ADCs Have a Challenging History in Lung Cancer

TROP2-targeted ADCs attract considerable interest in many solid tumors. Their path in lung cancer, however, has not been straightforward. Some TROP2 ADC studies did not fully meet expectations; the clinical weight of PFS and OS gains was particularly debated in unselected advanced NSCLC populations. The positive phase 3 result of OptiTROP-Lung05 may therefore be an important signal of renewed confidence not only for sacituzumab tirumotecan but also for the TROP2 ADC class.

Pharmaceutical features that distinguish Sac-TMT include TROP2 targeting, a belotecan-derived topoisomerase I inhibitor payload, a pH-sensitive linker, and a high drug-to-antibody ratio. What matters most clinically, however, is whether these technological differences translate into patient outcomes. OptiTROP-Lung05 shows that this translation is strong at the PFS level.

Priority Review Has Begun in China; OS and Approval Processes Will Be Awaited for a Global Standard

According to Kelun-Biotech, a supplemental new drug application for sacituzumab tirumotecan + pembrolizumab was accepted by China's National Medical Products Administration and granted priority review. The application concerns the first-line treatment indication in locally advanced or metastatic NSCLC with PD-L1 TPS ≥1, negative EGFR, and negative ALK.

Nevertheless, several factors will determine the impact on global clinical practice: maturation of OS data, validation of the safety profile in different populations, authorization processes in different regions, the need for direct rather than indirect comparisons with pembrolizumab + chemotherapy or other chemo-immunotherapy standards, and cost-effectiveness assessments.

Adding a Targeted Cytotoxic Payload to Immunotherapy May Open a New Chapter in First-Line NSCLC

Stronger Disease Control, Closer Monitoring of Adverse Effects

OptiTROP-Lung05 May Begin an Era of ADC + Immunotherapy in First-Line Lung Cancer

OptiTROP-Lung05 showed that sacituzumab tirumotecan + pembrolizumab provided strong PFS superiority over pembrolizumab monotherapy in PD-L1 TPS ≥1, EGFR/ALK-negative advanced NSCLC. Median PFS had not yet been reached in the combination arm, whereas it was 5,7 months in the pembrolizumab arm; HR 0,35 and P<0,0001 demonstrate that the difference is statistically very strong.

The response rate was also markedly higher: ORR was 70,2% versus 42,0%. Deep response rates were reported as 49,0% versus 25,9%. Although OS data are not yet mature, the early trend appears to favor the combination. Conversely, because grade ≥3 adverse effects were higher in the combination arm, the efficacy gain and burden of toxicity should be assessed together.

This study brings a new class combination into consideration for first-line treatment in advanced NSCLC: immunotherapy + a TROP2-targeted ADC. If the favorable signal is maintained when OS data mature and safety remains manageable, sacituzumab tirumotecan + pembrolizumab may become a new treatment paradigm, particularly in PD-L1-positive patients in whom adequate control with immunotherapy alone is difficult.