Insilico Medicine’s experimental mesothelioma drug, ISM6331, has reached another important milestone. Early clinical trial results show signs that it may help shrink tumors in patients who’ve already received other treatments.
On October 25, 2026, researchers presented the drug’s first human trial results at the European Society for Medical Oncology (ESMO) Congress in Madrid, Spain. The findings come just months after ISM6331 received Fast Track Designation from the U.S. Food and Drug Administration (FDA).
The results offer new hope for patients with mesothelioma, although larger studies are still needed to confirm how well the drug works.
Phase 1 ISM6331 Results Presented at ESMO 2026
Researchers shared early results from an ongoing phase 1 clinical trial involving 36 patients with mesothelioma or other advanced cancers. Participants received daily doses of ISM6331 ranging from 15 mg to 130 mg and had previously undergone treatment.
The findings showed several encouraging results for mesothelioma patients:
- 40% response rate at the highest dose: Two of five patients receiving 130 mg had measurable tumor shrinkage.
- 18.2% response rate across evaluated doses: Four of 22 mesothelioma patients receiving 30-130 mg had partial responses.
- 68.2% disease control rate: About two-thirds of these 22 patients had tumors that shrank or remained stable at their first assessment.
- Some early and lasting responses: Three of the four patients who responded showed improvement on their first scans after eight weeks. Three responses were still ongoing when researchers collected the data, including one lasting nearly a year.
These findings suggest that ISM6331 may help some patients whose cancer hasn’t responded to earlier mesothelioma treatments. However, the study is still ongoing, and researchers need more data to confirm these results.
Get our Free Mesothelioma Guide now to learn more about different treatments that could help you or someone you love.
What Did Researchers Find About ISM6331’s Safety?
The phase 1 trial also provided early information about ISM6331’s safety. Researchers reported no dose-limiting toxicities at the doses studied, and no patients stopped treatment because of treatment-related side effects.
Most side effects were mild to moderate. However, 8.3% of participants experienced more serious side effects, including fatigue, skin inflammation, or elevated pancreatic enzyme levels.
Researchers also found that 11.1% of patients developed protein in their urine, a condition called proteinuria. All reported cases were mild and reversible.
What Do These Results Mean for Mesothelioma Patients?
The findings suggest ISM6331 could eventually offer another treatment option for patients whose cancer has progressed despite other therapies.
“The 40% ORR at 130 mg and manageable safety profile in previously treated mesothelioma support continued investigation.”
– Halle Zhang, PhD (Med), Vice President of Clinical Development – Oncology at Insilico Medicine
Zhang also confirmed that the company plans to evaluate doses further before moving toward a randomized phase 2a study.
Still, these findings are preliminary. The 40% response rate at the highest dose came from just five evaluable patients, and larger studies are needed to determine how long the drug’s benefits last and whether it can help patients live longer.
ISM6331 remains experimental and hasn’t received FDA approval to treat mesothelioma.
FDA Grants ISM6331 Fast Track Designation
On July 29, 2026, Insilico Medicine announced that the FDA granted ISM6331 Fast Track Designation for advanced mesothelioma. It was the company’s first drug to receive this designation.
Fast Track status helps speed up the development and review of promising new treatments for serious diseases with unmet medical needs.
The designation allows Insilico to work more closely with the FDA and could lead to a faster review if future trials continue to show positive results. However, Fast Track status doesn’t guarantee approval.
What Is ISM6331?
ISM6331 is an experimental cancer drug taken orally and developed by Insilico Medicine using its artificial intelligence (AI) drug discovery platform, Chemistry42.
Unlike traditional chemotherapy, ISM6331 targets specific proteins involved in cancer cell growth.
Researchers are studying the drug in patients with advanced mesothelioma and other solid tumors, including cancers that haven’t responded to previous treatments.
How Does ISM6331 Work?
Cancer cells rely on signals that tell them when to grow and divide. ISM6331 aims to block proteins called TEAD, which help control some of those signals.
TEAD proteins are part of the Hippo signaling pathway, a system that normally helps regulate cell growth.
In some cancers, including mesothelioma, changes in this pathway can allow cells to grow uncontrollably. By blocking TEAD activity, researchers hope ISM6331 can slow tumor growth.
Scientists are also exploring whether drugs that target TEAD could eventually work alongside other treatments, such as chemotherapy or immunotherapy.
More research is needed before doctors can determine whether these combinations would benefit patients.
ISM6331 Treatment Timeline
ISM6331 has made several advances since its development began, including special FDA designations and its progression into human clinical trials.
Here’s a look at the major milestones:
- September 2020: Insilico launches Chemistry42, the AI platform later used to develop ISM6331.
- June 2023: Insilico selects ISM6331 for further preclinical development.
- April 2024: Insilico presents findings from laboratory and animal studies at the American Association for Cancer Research (AACR) Annual Meeting.
- June 2024: The FDA grants ISM6331 Orphan Drug Designation for mesothelioma.
- August 2024: ISM6331 receives FDA clearance to begin clinical testing in humans.
- January 2025: The first patient receives ISM6331 in a phase 1 clinical trial.
- July 27, 2026: Insilico announces that early trial results will be presented at ESMO Congress 2026.
- July 29, 2026: The FDA grants ISM6331 Fast Track Designation for advanced mesothelioma.
- October 25, 2026: Researchers present the first human trial results at ESMO 2026, reporting tumor responses in some patients with advanced mesothelioma.
The October results give researchers their first public human trial findings to help guide the next stage of ISM6331’s development.
What’s Next for ISM6331?
Following the ESMO presentation, Insilico Medicine announced plans to continue studying ISM6331 to determine the most appropriate dose for future trials.
Depending on the results, the company hopes to begin a randomized phase 2a study comparing different doses in mesothelioma patients.
This next phase could provide more information about the drug’s effectiveness and safety, bringing researchers closer to determining whether ISM6331 could become a new treatment option.
Get Help Accessing Mesothelioma Treatment
New therapies like ISM6331 could eventually give mesothelioma patients more options, especially when other treatments have stopped working.
Although ISM6331 is still being studied, a mesothelioma specialist can help you explore available treatments and clinical trials that may be right for you.
Top mesothelioma doctors can help by:
- Assembling a care team of nurses and cancer specialists
- Creating a treatment plan tailored to your diagnosis
- Recommending clinical trials that may be a good fit
Mesothelioma Hope can match you with a specialist and help you prepare for your first appointment. Call a Patient Advocate at (866) 608-8933 or request our Free Mesothelioma Guide to get started.
