Rezubio doses first patients in phase I trial of inhaled respiratory drug RZ-520

The company said RZ-520 has been designed to maintain drug exposure within the lungs while limiting systemic distribution

Chinese biotech player Rezubio has dosed the first cohort of patients in a Phase I clinical trial of RZ-520, an inhaled therapeutic candidate being developed for chronic respiratory diseases, following investigational new drug (IND) clearances from China’s National Medical Products Administration (NMPA) and the US Food and Drug Administration (FDA).

The Phase I study is evaluating the pharmacodynamics, pharmacokinetics, safety and tolerability of RZ-520 in healthy volunteers as the company advances the candidate into clinical development.

RZ-520 is the second drug candidate from Rezubio’s Membrane-Anchored Drug Design (MADD) platform to enter clinical testing. The platform is designed to develop tissue-targeted therapies that remain locally active for longer periods, with potential applications involving cell surface proteins in the gastrointestinal and respiratory tracts.

The company said RZ-520 has been designed to maintain drug exposure within the lungs while limiting systemic distribution. The approach is intended to potentially improve efficacy and safety while offering greater dosing convenience for patients with chronic respiratory conditions.

In preclinical studies, RZ-520 demonstrated therapeutic activity across multiple disease models and showed limited systemic exposure. However, these findings remain at the preclinical stage and have yet to be validated in human clinical trials.

Yusheng Xiong, CEO of Rezubio, said the dual IND clearances from the FDA and NMPA, along with the first cohort dosing, represent a milestone for both the RZ-520 programme and the company’s MADD platform.

“Advancing our second MADD-derived drug candidate into clinical development further validates the power of our platform to design tissue-targeted therapies that address a broad spectrum of challenging diseases,” Xiong said.

The company plans to continue the clinical development of RZ-520 and assess its potential as a differentiated treatment option for patients with chronic respiratory diseases.

Rezubio raised $20 million in a Series A financing round in December 2025, led by Lapam Capital with participation from Riverhead Capital and Frees Fund. The funding was intended to support the advancement of the company’s lead programme into Phase II clinical development for diabetes and obesity.