At the 2024 American Society of Clinical Oncology (ASCO) Annual Meeting held in Chicago, USA, from May 31 to June 4, Mabwell's 9MW2821, a novel Nectin-4-targeting ADC, was showcased for its multi-cancer efficacy. The oral presentation, encapsulated under the abstract number 3013, was conducted by Professor Jian Zhang from Fudan University Shanghai Cancer Center, with key highlights as below:

Background: 

9MW2821 is a monoclonal ADC that delivers monomethyl auristatin E to cells expressing Nectin-4. Nectin-4 is an adhesion molecule that highly expressed in variety of solid tumors, especially urothelial cancer (UC), cervical cancer (CC), esophageal cancer (EC) and breast cancer.

Methods: 

9MW2821 was administered by intravenous infusion at doses of 0.33-1.5mg/kg on days 1, 8 and 15 of each 28-day cycle. The study included dose escalation, dose expansion and cohort expansion period which included UC, CC, EC, triple negative breast cancer (TNBC) and other Nectin-4 positive solid tumors that progressed after ≥1 systemic treatments (Tx). Primary objectives were assessment of safety and preliminary efficacy.

Results: 

As of Jan 15, 2024, 260 patients (pts) were enrolled with doses ranging from 0.33 to 1.5mg/kg. Only 1 out of 6 pts in 1.5mg/kg group had dose limiting toxicity (grade 4 neutropenia lasted more than 5 days). The maximum tolerated dose was not reached up to 1.5mg/kg and the RP2D was selected as 1.25mg/kg for tolerance.

37 UC pts, 45 CC pts, 27 EC pts and 16 TNBC pts were enrolled at 1.25mg/kg and evaluable for tumor assessment. Median prior lines of Tx were 2 (range, 1-4).

Of the 37 UC patients evaluable for efficacy assessment, the objective response rate (ORR) and disease control rate (DCR) were 62.2% and 91.9%, respectively, with median progression-free survival (mPFS) was 8.8 months and median overall survival (mOS) was 14.2 months.

Of the 53 CC patients evaluable for efficacy assessment, 51% were previously treated with platinum-based doublet chemotherapy and bevacizumab, and 58% received platinum-based doublet chemotherapy and immune checkpoint inhibitor, with ORR and DCR were 35.8% and 81.1%, respectively. The mPFS was 3.9 months, with mOS not reached. Of the patients with Nectin-4 tumor cell staining intensity 3+, the ORR was 43.6% among the 39 evaluable patients.

Of the 39 EC patients evaluable for efficacy assessment, ORR and DCR were 23.1% and 69.2%, respectively, with mPFS of 3.9 months and mOS of 8.2 months; 37 of them were treated with platinum-based chemotherapy and immunotherapy previously.

Of the 20 patients with locally advanced or metastatic triple-negative breast cancer and evaluable for efficacy assessment, the ORR and DCR were 50.0% and 80.0% respectively. The mPFS was 5.9 months, and the mOS was not yet reached, with one patient achieved complete response (CR) and had been in CR for 20 months and is currently sustained to be CR. 

240 pts were enrolled at dose of 1.25mg/kg. The most common TRAEs of 1.25mg/kg dose group (≥20%, all grade/≥5%, ≥G3) were white blood cell (WBC) count decreased (50.8%, 23.3%), neutrophil count decreased (46.3%, 27.9%), anemia (43.8%, 8.3%), aspartate aminotransferase increased (42.1%, 2.9%), alanine aminotransferase increased (35.4%, 2.1%), asthenia (32.1%, 2.9%), rash (30.0%, 5.0%), decreased appetite (28.8%, 1.3%), nausea (26.7%, 0%), hyperglycemia (25.4%, 2.1%), platelet count decreased (24.2%, 4.6%), alopecia (24.2%, 0%), hypoaesthesia (22.5%, 1.7%), constipation (21.3%, 0%), vomiting (20.9%, 1.3%), hypertriglyceridemia (20.4%, 2.1%), gamma-glutamyltransferase increased (15.8%, 5.4%).

Conclusions: The data indicated encouraging efficacy of 9MW2821 in advanced UC, CC, EC and TNBC. 9MW2821 is the first Nectin-4 targeting ADC showed antitumor activity in patients with CC, EC and TNBC. The safety profile showed adequate tolerability.

About 9MW2821

9MW2821 is the first site-specific conjugated novel Nectin-4-targeting ADC developed by Mabwell using ADC platform and automated high-throughput hybridoma antibody molecular discovery platform, and is the first drug candidate to enter clinical study among the Nectin-4-targeting ADCs developed by Chinese companies, and the first therapeutic drug candidate targeting Nectin-4 in the world to reveal clinical efficacy data of cervical cancer, esophageal cancer and breast cancer. 9MW2821 has been granted Fast Track Designation (FTD) for the treatment of advanced, recurrent, or metastatic esophageal squamous cell carcinoma in Feb. 2024, and also successively granted Orphan Drug Designation (ODD) and FTD for the treatment of esophageal cancer and recurrent or metastatic cervical cancer progressed on or following prior treatment with a platinum-based chemotherapy regimen in May 2024.

9MW2821 achieves site-specific modification of antibody through proprietary conjugate technology linkers and optimized ADC conjugation process. After injection, 9MW2821 can specifically bind to Nectin-4 on the cell membrane surface, be internalized and release cytotoxic drug, and induce the apoptosis of tumor cells.