Pembrolizumab Biosimilar Meets Primary Phase 1 and Phase 3 End Points in NSCLC

SB27, a proposed pembrolizumab (Keytruda) biosimilar, has met the primary pharmacokinetic (PK) and efficacy end points of both its phase 1 (NCT06268613) and phase 3 (NCT06348199) studies, respectively, according to preliminary topline data.¹

The pivotal phase 3 study demonstrated an equivalent objective response rate (ORR) at week 24 between SB27 and the reference product. The 90% CI for the ORR ratio between SB27 and Keytruda was 0.737 to 1.071, falling entirely within the prespecified equivalence margin of 0.712 to 1.405.

Safety, PK, and immunogenicity profiles were also reported as comparable between arms. In the phase 1 study, the area under the curve–based equivalence criteria were met across all 3 treatment arms; no further PK parameters, such as C_max or half-life, were reported at this stage.

Full data from both studies are expected to be available upon study completion later in 2026. Should these data support a regulatory submission and subsequent approval, SB27 would enter a biosimilar landscape for pembrolizumab that, as of mid-2026, remains nascent despite the reference product's extensive use across multiple tumor types.

“We are excited to announce preliminary results from the phase 1 and phase 3 studies for SB27, our pembrolizumab biosimilar candidate. These topline positive results reinforce our scientific expertise and leadership in biosimilar development,” Donghoon Shin, executive vice president and head of the Clinical Sciences Division at Samsung Bioepis, stated in a news release.¹ “We are on track to complete both phase 1 and phase 3 studies within [2026]. Leveraging our robust quality management system, we remain committed to advancing our biosimilar portfolio to broaden access to lifesaving biologic medicines for patients with unmet needs.”

Of note, pembrolizumab was originally approved by the FDA in 2014 and has since accumulated approvals across more than 30 indications spanning melanoma, non–small cell lung cancer (NSCLC), head and neck squamous cell carcinoma, and numerous other tumor types.^1,2

How was the phase 3 study designed?

The phase 3 study was a randomized, double-blind, parallel-group, multicenter trial that enrolled 555 patients with metastatic nonsquamous NSCLC.^1,3

Patients were randomly assigned to receive either SB27 or pembrolizumab in combination with pemetrexed and carboplatin, with carboplatin administered for the first 4 cycles only, every 3 weeks for up to 48 weeks. The primary end point was ORR at week 24, assessed within a prespecified equivalence margin. Secondary end points included safety, PK, and immunogenicity.

How was the phase 1 study designed?

The phase 1 PK study was a randomized, double-blind, 3-arm, parallel-group, multicenter trial that included 163 patients with stage II or IIIA NSCLC following complete resection and adjuvant platinum-based chemotherapy.^1,4

Patients were randomly assigned to receive SB27, European Union (EU)–sourced pembrolizumab, or US-sourced pembrolizumab every 3 weeks for up to 51 weeks, with serial blood sampling for PK analysis.

The primary end point was PK bioequivalence, assessed by area under the curve. The preliminary evaluation indicated that drug exposure met the predefined equivalence criteria across all 3 arms. The 3-arm design—comparing the proposed biosimilar with both EU- and US-sourced reference products—is consistent with standard regulatory expectations for biosimilar PK bridging studies intended to support multiregional submissions.

References

1. Samsung Bioepis announces positive preliminary phase 1 and phase 3 data for SB27, a proposed biosimilar to Keytruda (pembrolizumab). News release. Samsung Bioepis; 2026. Accessed June 2026. https://www.samsungbioepis.com/en/newsroom/newsroomView.do?idx=566&currentPage=1
2. Merck receives accelerated approval of Keytruda (pembrolizumab), the first FDA-approved anti-PD-1 therapy. News release. Merck. September 4, 2014. Accessed June 29, 2026. https://www.merck.com/news/merck-receives-accelerated-approval-of-keytruda-pembrolizumab-the-first-fda-approved-anti-pd-1-therapy/
3. A study to compare the efficacy, safety, pharmacokinetics, and immunogenicity between SB27 and Keytruda in subjects with metastatic non-squamous non-small cell lung cancer. ClinicalTrials.gov. Updated May 5, 2026. Accessed June 30, 2026. https://clinicaltrials.gov/study/NCT06348199
4. A study to compare the pharmacokinetics, efficacy, safety, and immunogenicity of pembrolizumab (SB27, EU sourced Keytruda, and US sourced Keytruda) in subjects with stage II–IIIA NSCLC following complete resection and adjuvant platinum-based chemotherapy. ClinicalTrials.gov. Updated May 5, 2026. Accessed June 30, 2026. https://clinicaltrials.gov/study/NCT06268613