Idiopathic pulmonary fibrosis kills most patients within three to five years of diagnosis. There is no cure. The two approved treatments slow the scarring but do not stop it, and both carry significant side effects that limit tolerability.
Rentosertib was designed by an AI. Not assisted by an AI. Designed by one, from target identification through molecule structure. Phase IIa data showed dose-dependent efficacy improvements with good tolerability. Phase III is coming in the second half of 2026.
On April 28, 2026, Insilico Medicine (HKEX: 3696) announced that the inhalation formulation of Rentosertib has received IND clearance from China’s Center for Drug Evaluation, making it the world’s first AI-designed drug candidate to enter a direct-to-lung clinical study. It is also the 13th program from Insilico’s AI pipeline to receive IND clearance.
Why an inhalation formulation is a meaningful advance over oral dosing
IPF is a lung disease. The fibrosis occurs in lung tissue. Getting therapeutic concentrations to that tissue through oral administration requires the drug to absorb through the gut, enter systemic circulation, and distribute to the lungs. Only a fraction of the oral dose reaches the target organ. The systemic exposure that comes with oral administration is what generates most of the side effects that cause patients to reduce or discontinue treatment.
Inhalation delivers the drug directly to the respiratory tract. Preclinical studies showed the inhalation formulation achieves higher lung exposure with low systemic exposure, with antifibrotic and anti-inflammatory efficacy in animal models. The practical consequence, if those findings translate to human trials, is more drug where it is needed at lower total doses, with less systemic exposure causing side effects elsewhere.
Insilico’s co-CEO Feng Ren described the goal precisely: targeted lung delivery to achieve higher pulmonary exposure and faster onset at lower doses while reducing systemic exposure and optimizing the benefit-risk profile.
The Phase I study will enroll approximately 80 subjects across two parts. The first is a randomized, double-blind, placebo-controlled trial in healthy volunteers with single and multiple ascending dose cohorts. The second is an open-label evaluation in IPF patients receiving multiple doses. The Phase I data will establish the safety, tolerability, and pharmacokinetic profile of the inhalation formulation before progressing.
What Rentosertib is and why it matters for the IPF field
Rentosertib is a TNIK inhibitor. TNIK, or TRAF2 and NCK-interacting kinase, is a signaling protein involved in the Wnt pathway that drives fibrotic tissue remodeling. Insilico’s AI platform identified TNIK as a therapeutic target for IPF and designed the inhibitor molecule. The entire early discovery and development process was completed in 18 months using fewer than 80 molecules synthesized and tested.
Traditional drug discovery typically requires 4.5 years and thousands of compounds screened to reach a preclinical candidate nomination. Insilico’s process took less than two years and a fraction of the compounds. The workflow was published in Nature Biotechnology in March 2024. The Phase IIa results demonstrating proof of concept for AI-designed drug efficacy were published in Nature Medicine in June 2025.
FDA has granted Rentosertib Orphan Drug Designation for IPF. China’s CDE granted Breakthrough Therapy Designation in May 2025. Both designations reflect regulatory recognition that the drug addresses a serious unmet need with preliminary evidence of substantial clinical improvement over available therapy.
According to the American Lung Association’s IPF research summary, approximately 100,000 people in the United States live with IPF, with 30,000 to 40,000 new cases diagnosed annually. Globally, the disease affects approximately 5 million people. Median survival from diagnosis is three to four years. The two currently approved treatments, nintedanib and pirfenidone, reduce the rate of lung function decline but do not halt progression and are poorly tolerated by a significant proportion of patients.
A first-in-class TNIK inhibitor that addresses a novel mechanistic pathway, with an inhalation formulation designed to improve the benefit-risk profile, enters that unmet need with a mechanism that is genuinely differentiated from what exists.
The 13-program milestone and what it signals
Insilico has now achieved IND clearance for 13 programs across fibrosis, oncology, immunology, and central nervous system disorders. It has nominated 30 preclinical candidates total. Three Phase II trials are underway. The company has drug discovery partnerships with Eli Lilly, Sanofi, Qilu Pharmaceutical, and others.
The reproducibility argument is the one that matters for evaluating AI-driven drug discovery as a platform rather than a one-off success. A single clinical milestone could be coincidence. Thirteen IND clearances across multiple disease areas, with a Phase IIa publication in Nature Medicine showing dose-dependent efficacy, begins to look like a systematic capability rather than luck.
Whether that capability consistently produces approved drugs depends on the Phase III data for oral Rentosertib expected later in 2026 and the clinical results that follow across the pipeline.
Sources
- American Lung Association — IPF Research Summary
- Nature Medicine — Rentosertib Phase IIa Results
- Insilico Medicine — Official Website
Editorial disclosure
This article is based on a press release issued by Insilico Medicine and has been independently rewritten and editorially expanded. It covers IND clearance for Rentosertib inhalation solution from China’s Center for Drug Evaluation. Insilico Medicine trades on the Hong Kong Stock Exchange under 3696.HK. Rentosertib is an investigational drug that has not received regulatory approval for any indication. IND clearance permits clinical study initiation and does not indicate efficacy or safety. Phase I enrollment has not yet commenced. Phase II oral Rentosertib results are preliminary and Phase III initiation is targeted for H2 2026. Clinical stage biotechnology investments carry significant risk. This article does not constitute medical or investment advice. Market context is sourced from the American Lung Association. Commentary reflects the author’s own assessment. The information provided on this website is for informational and educational purposes only. Our content is derived strictly from verified online sources to ensure accuracy and objectivity. This analysis does not constitute financial, investment, or professional advice. Readers are encouraged to consult with qualified professionals before making decisions based on this information. For more information, please see our full DISCLAIMER.
