ИСТИНА

Abstract 1100P Background In a phase III multi-center randomized open-label study BCD-217-3/NEO-MIMAJOR (NCT05751928) a treatment option without lymphadenectomy was investigated. The study drug BCD-217 is a fixed-dose combination of nurulimab (aCTLA-4, 5 mg/ml) and prolgolimab (aPD-1, 15 mg/ml) was recently approved as the 1st line treatment for metastatic melanoma. Here we present the primary interim analysis of the pathological response rate and safety of BCD-217 in neoadjuvant systemic therapy (NAST) arm. Methods Pts with respectable stage III melanoma were randomized in 2 treatment arms: BCD-217 arm and CLND + adjuvant pembrolizumab arm. In NAST arm pts received 2 infusions Q3W of 0.2 ml/kg BCD-217. Pts with complete or near complete pathological response (pCR or pnCR) continued with adjuvant aPD1 prolgolimab 250 mg Q3W up to 12 mos, pts not responded to NAST underwent CLND and continued the same adjuvant therapy. pCR was assessed using samples from the index lymph node resection according to International Neoadjuvant Melanoma Consortium (INMC) guidelines. Results At the cut-off 15th of Apr’24 108 pts with resectable stage III melanoma (III С/D-71.3% pts) were randomized in 2 treatment arms: NAST arm (n=57) and AT (n=51). For a median follow-up of 2.8 mos 43/57 (75.4%) pts of NAST arm undergo index lymph node resection for pCR assessment. 22/57 (38.6%) pts met pCR/pnCR criteria (ITT). Only 4/57 (7%) pts in the BCD-217 arm had radiological disease progression, 2/57 (3.5%) pts died (one before and one after 1st infusion). 35/55 (63.6%) pts in the BCD-217 arm had any grade (Gr) AEs, 4/55 (7.3%) had severe (3-5 Gr) AEs, 21/55 (38.2%) pts had irAEs (3 Gr - 1/55 (1.8%)) from the pts who received at least one administration or surgery. Surgery-related AEs (all Gr 1-2) were observed in 8/55 (14.5%) pts. No pts required therapy discontinuation due to AEs. Conclusions The presented data shows that 2 cycles of BCD-217 are enough to achieve pCR and potentially avoid CLND in ∼40% pts. pCR/pnCR can be recognized as a hallmark of OS/DFS improvement according to INMC. There were no severe irAEs or treatment-related AEs. The study population in BCD-217-3/NEO-MIMAJOR initially had a worse prognosis compared to the similar trials. Clinical trial identification NCT05751928. Editorial acknowledgement Legal entity responsible for the study JSC BIOCAD. Funding JSC BIOCAD. Disclosure I. Sorokina, Y. Linkova, A.V. Zinkina-Orikhan, A. Siliutina, F. Kriukov: Financial Interests, Personal, Sponsor/Funding: Biocad. All other authors have declared no conflicts of interest.