FDA Grants Fast Track Status to SBE303 in Urothelial Cancer

The FDA granted fast track designation to SBE303, an investigational antibody-drug conjugate (ADC) developed by Samsung Bioepis, for patients with locally advanced or metastatic urothelial cancer previously treated with enfortumab vedotin (Padcev).¹

SBE303 is the company's first novel ADC and is being evaluated in a phase 1 clinical trial (NCT07524348). The designation is intended to facilitate the development and regulatory review of therapies that address unmet medical needs in serious conditions.

This designation establishes an important regulatory framework for our program, enabling closer dialogue and more frequent interactions with the Agency as our global Phase 1 study advances,” Jung said in a news release. “We look forward to working collaboratively with the FDA to guide our clinical development program efficiently and advance SBE303 through each stage of evaluation,” said Byoungin Jung, vice president and regulatory affairs team leader at Samsung Bioepis, in a news release.

Study Design

The phase 1, open-label study is enrolling patients with histologically confirmed, locally advanced unresectable or metastatic solid tumors with recurrence or progression after standard therapy, intolerance to standard therapy, or when no standard therapy is available.² The study is active at 7 locations in Arizona and Virginia in the US as well as Australia, South Korea, and Spain.

Patients cannot have spinal cord compression or clinically active central nervous system metastases, leptomeningeal disease, thromboembolic or clinically significant bleeding events, significant cardiovascular disease, or an active autoimmune disorder.

All patients in the study receive an intravenous infusion of SBE303. The primary end points are incidence of adverse events (AEs) and serious AEs, incidence of dose-limiting toxicities, and confirmed objective response rate. Second end points include tumor response, disease control rate, and pharmacokinetics.

SBE303 Targets Nectin-4 in Urothelial Cancer

SBE303 is designed to target Nectin-4, a cell adhesion protein expressed in several tumor types, including urothelial cancer. The investigational ADC combines an anti–Nectin-4 antibody with a topoisomerase I inhibitor payload through a proprietary linker.¹

The company said the investigational new drug was engineered to improve the therapeutic window associated with Nectin-4–targeting ADCs, which can be restricted by dose-limiting toxicities.

Nectin-4 has emerged as a therapeutic target in urothelial cancer. Enfortumab vedotin, an approved Nectin-4–directed ADC, has demonstrated clinical benefit in advanced disease.³ The combination of enfortumab vedotin and pembrolizumab (Keytruda) has also demonstrated improved survival compared with chemotherapy in previously untreated locally advanced or metastatic urothelial cancer.⁴

Samsung Bioepis plans to continue advancing SBE303 through its phase 1 clinical development program.

REFERENCES

1. Samsung Bioepis receives FDA fast track designation for SBE303, company's first antibody-drug conjugate candidate. October 21, 2026. https://tinyurl.com/y9h8zzp9

2. A trial to investigate the safety of E303 in participants with advanced refractory solid tumors. ClinicalTrials.gov. Updated October 1, 2026. Accessed October 22, 2026. https://clinicaltrials.gov/study/NCT07524348

3. Hatakeyama S, Ozaki K, Yamamoto H, et al Real-world analysis of the efficacy and safety of enfortumab vedotin in patients with locally advanced or metastatic urothelial carcinoma: A multicenter retrospective study. J Clin Oncol. 43, 2025 (suppl 5; abstract 712)

4. Gupta S, Loriot T, Van der Heijden M, et al. Patient-reported outcomes (PROs) from a randomized, phase 3 trial of enfortumab vedotin plus pembrolizumab (EV+P) versus platinum-based chemotherapy (PBC) in previously untreated locally advanced or metastatic urothelial cancer (la/mUC). Presented at: 2024 American Society for Clinical Oncology Annual Meeting. May 31-June 4, Chicago, Illinois. Abstract 4502.