The U.S. biotech company Adcentrx Therapeutics announced yesterday that the first patient has been dosed in a Phase 1a/b trial testing its potential first-in-class antibody-drug conjugate, ADRX-0405, for the treatment of advanced solid tumors. This follows the FDA clearance for its IND application in October 2024.
Antibody-drug conjugates are composed of an antibody attached to a cytotoxic payload. In the case of ADRX-0405, a humanized antibody is linked to a topoisomerase inhibitor payload. This payload blocks the enzyme topoisomerase, which cancer cells require to divide and grow.
The antibody in ADRX-0405 specifically targets six-membrane epithelial antigen of the prostate 1 (STEAP1), a protein found on the surface of cells. STEAP1 is highly expressed in prostate and other cancers, including lung, colorectal, and gastric cancer.
“Advancing our second program into clinical trials marks an important milestone for Adcentrx and further validates the potential of our ADC technology platform,” said Hui Li, Founder and CEO of Adcentrx in a press release.
“STEAP1 is an attractive ADC target, and we are excited about the first-in-class potential for ADRX-0405. We believe this novel ADC offers a unique approach to treating patients with STEAP1-expressing cancers, such as metastatic castration-resistant prostate cancer, where a significant unmet need remains for new targeted therapies.”
Preclinical studies have confirmed a positive pharmacokinetics and safety profile of ADRX-0405, as well as significant efficacy across several tumor models.
The ADRX-0405 Phase 1a/b study is an open-label dose escalation and dose expansion trial, conducted across the U.S. in patients with select advanced solid tumors. The study aims to analyze the safety and tolerability of ADRX-0405 and will allow the researchers to determine the optimal dose. Adcentrx plans to publish initial data in the last quarter of 2025.
ADRX-0405 is Adcentrx’s second ADC in clinical development. In December 2024, the company announced that it had dosed the first patient in a Phase 1b trial, an ongoing Phase 1a/b study of ADRX-0706, an ADC targeting Nectin-4, for the treatment of advanced solid tumors.
At the time, Li said in a press statement: “Encouraging findings from our Phase 1a trial demonstrate the best-in-class potential for ADRX-0706, with differentiated safety and pharmacokinetic properties, including a much lower incidence of critically meaningful adverse events for patients, such as peripheral neuropathy. Additionally, the preliminary efficacy responses observed across different dose levels and tumor types provide important clinical validation of Adcentrx’s ADC platform[...]”
