Double-blind Study to Evaluate the PK, Efficacy, Safety and Immunogenicity of MB12 Versus Keytruda® in Stage IV NSCLC

MB12 is being developed by mAbxience Research S.L., and its clinical development is sponsored by Laboratorio Elea Phoenix S.A. as a proposed biosimilar to Keytruda®. The reference medicinal product is European Union (EU)-sourced Keytruda®, manufactured and marketed by Merck Sharp & Dohme. Study drugs: MB12 and Keytruda® Study drug administration: intravenous infusion Dosing instructions: 200 mg administered over 30 minutes, every 3 weeks The study will consist of 2 periods defined as follows: - Main Study Period from Screening up to Cycle 6 included. - Extended Treatment Period from Cycle 7 up to Week 52 for those subjects who demonstrate clinical benefit from the treatment (CR, PR, and SD). They will continue treatment until disease progression, intolerance to the study drug, treatment discontinuation for other reason, or up to Week 52, whichever occurs first. The anti-tumor activity will be determined by local radiological examination for all measurable and evaluable lesions according to RECIST version 1.1. During the Main Study Period, the efficacy assessments will be performed every 6 weeks from the first infusion (Cycle 1, Day 1). During the Extended Treatment Period, the assessments will be performed every 9 weeks, from Week 18 onwards, according to RECIST criteria, until disease progression, intolerance to the study drug, treatment discontinuation for other reason, or up to 52 weeks, whichever occurs first. Safety assessments include vital signs, physical examination, ECOG performance status, 12-lead ECGs, clinical laboratory assessments (hematology, clinical chemistry, thyroid function, coagulation, virology, urinalysis, and pregnancy tests), and AE assessments. The primary PK parameter is AUCss at Cycle 6. Serum concentrations used for estimating AUCss will be determined by a validated analytical procedure once steady state (5 elimination half-lives) has been reached. Secondary PK parameters, including maximum concentration (Cmax), minimum concentration (Ctrough), time to maximum concentration (tmax), clearance (CL), elimination half-life (t1/2), and volume of distribution (Vss), will be calculated for Cycle 1 and Cycle 6, as applicable. Additional PK parameters may be included if deemed appropriate. PK variables will be calculated according to the recommendations of the European Medicines Agency (EMA) and the World Health Organization (WHO). Blood samples for PK analysis will be collected at Cycle 1 and Cycle 6 as follows: predose; at 30 minutes after the SOI; at 4, 6, 24, 48, 168, 336, and 504 hours after the SOI. The comparison of the immunogenicity profile of MB12 versus Keytruda® during the Main Study and Extended Treatment Periods include: - ADAs - Nabs in ADA (+) samples - Titers in ADA (+) samples During the Main Study Period, blood samples for immunogenicity will be collected pre-dose at Cycle 1 Day 1, Cycle 1 Day 14, pre-dose at Cycle 3 Day 1, and pre-dose at Cycle 6 Day 1. During the Extended Treatment Period, 2 additional samples will be collected in those subjects who continue treatment after Cycle 6 at Week 26 and at Week 52 or EOT/early termination (if this occurs before Week 52 and if previous sample has not been taken within the last 16 weeks).