Phase 2a trial testing mRNA therapy in cystic fibrosis fully enrolled

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Developer Recode Therapeutics expects results by end of 2026

A Phase 2a clinical trial testing RCT2100, Recode Therapeutics’ investigational inhaled mRNA therapy for cystic fibrosis (CF), is fully enrolled, with results expected by the end of the year, the company announced.

The clinical updates were part of a broader company announcement focused on Recode’s CF programs, which also included new funding from the Cystic Fibrosis Foundation and a collaboration with an undisclosed gene-editing company to develop genetic medicines designed to correct mutations in CFTR, the gene that’s implicated in CF.

“We continue to make progress with the RCT2100 program, an inhaled mRNA therapy for cystic fibrosis. The Phase 2a study is ongoing with data expected in Q4, which will guide next steps for the program. Introducing gene editing adds another powerful path to develop therapies for patients still underserved by existing treatments,” Heather Clark, Recode’s new CEO, who formerly served as senior vice president and head of the CF franchise and the program management office, said in a company press release.

RCT2100 enables lung cells to produce working CFTR protein

CF is caused by mutations in the CFTR gene, which provides instructions for making a protein that helps regulate the movement of salt and water in and out of cells. When the CFTR protein is faulty or missing, thick and sticky mucus builds up in the lungs and other organs, driving many of the disease’s symptoms.

CFTR modulators can improve the function of certain faulty CFTR proteins, but not all people with CF are eligible for or able to take these medicines.

RCT2100 is designed to address that gap, providing an alternative to people who don’t respond or cannot tolerate CFTR modulators. The therapy works by delivering CFTR messenger RNA (mRNA) directly to lung cells, enabling them to produce a working CFTR protein. mRNA is a temporary molecule with genetic code that serves as a template for protein production.

The safety and tolerability of RCT2100 are currently being evaluated in a multipart Phase 2 clinical trial (NCT06237335). The first part of the trial assessed the therapy’s safety in healthy volunteers, who received single ascending doses of RCT2100 or a placebo. In the second part, adults with CF who cannot take CFTR modulators received multiple ascending doses of the therapy, given for up to 12 weeks. The third and final part, now underway, is focusing on assessing the safety and tolerability of RCT2100 when given alongside Vertex Pharmaceuticals’ Kalydeco (ivacaftor) to people with CF who are not eligible or not taking CFTR modulators.