Ateganosine Plus Cemiplimab Shows 90.5% Disease Control in Pretreated NSCLC

Investigational telomere-targeting agent ateganosine (THIO), given sequentially with the PD-1 inhibitor cemiplimab (Libtayo), produced a 90.5% disease control rate (DCR) in a heavily pretreated cohort of patients with advanced non–small cell lung cancer (NSCLC).¹

The interim data come from part C of the ongoing phase 2 THIO-101 trial (NCT05208944), an open-label, multicenter, dose-finding study evaluating ateganosine as third-line therapy in patients whose disease had progressed after prior checkpoint inhibitor treatment and chemotherapy.² Among 21 efficacy-evaluable patients who received at least 1 post-baseline tumor scan, 19 achieved disease control, defined as complete response, partial response, or stable disease. For comparison, standard third-line chemotherapy regimens are reported to yield DCRs of approximately 25% to 35%.¹

“The initial efficacy data from the part C studies are consistent with the encouraging efficacy signals we previously reported for parts A and B of THIO-101, including an 88% disease control rate in third-line [patients with] NSCLC. This measure of efficacy is close to triple the reported outcome for standard-of-care chemotherapy treatment,” said Vlad Vitoc, founder and CEO of MAIA Biotechnology, in a news release. “Importantly, patients enrolled in part C of our trial represent a more heavily pretreated population, with all patients having previously received docetaxel in addition to demonstrating resistance to both immunotherapy and other chemotherapies.”

Mechanism of Action

Ateganosine, also known by its research designations THIO and 6-thio-2′-deoxyguanosine, is a modified nucleotide designed to exploit telomerase activity in cancer cells. The compound is incorporated into telomeric DNA in a telomerase-dependent manner, triggering DNA damage responses and selective cancer cell death. Damaged telomeric fragments that accumulate in cytosolic micronuclei are thought to activate both innate immunity, via the cGAS/STING pathway, and adaptive T-cell responses. In preclinical models, sequential administration of ateganosine followed by a PD-(L)1 inhibitor produced sustained tumor regression, which investigators attributed to induction of cancer-specific immune memory. This rationale underlies the trial's dosing schedule, in which low-dose ateganosine is administered ahead of cemiplimab in 21-day cycles, with the goal of priming an antitumor immune response that the checkpoint inhibitor then sustains.

Safety

The company reported that the ateganosine-cemiplimab combination has shown an acceptable safety profile to date, including in this more heavily pretreated part C population, though detailed adverse event data were not published.

Trial Design

THIO-101 has 2 primary objectives: characterizing the safety and tolerability of ateganosine as both an anticancer agent and an immune-priming compound and assessing clinical efficacy using overall response rate as the primary end point. The expansion cohorts, including part C, are assessing overall response rate in third-line NSCLC patients resistant to prior checkpoint inhibitor and chemotherapy treatment.

Clinical Context

In June 2026, the FDA cleared an amended investigational new drug application for ateganosine, enabling MAIA Biotechnology, Inc to open enrollment at US clinical sites for the expansion of THIO-101. The clearance also incorporated updated manufacturing protocols, including new manufacturers, revised formulation parameters, and updated storage conditions for the investigational compound.³

In July 2025, the FDA granted fast track designation to the agent for the treatment of NSCLC that has progressed after immune checkpoint inhibitor therapy.⁴

REFERENCES

1. MAIA Biotechnology Reports Strong Initial Efficacy Data in Third-Line Non-Small Cell Lung Cancer from Phase 2 THIO-101 Part C Expansion Trial. News release. MAIA Biotechnology. July 8, 2026. Accessed July 8, 2026. https://tinyurl.com/49cvetbw

2. THIO Sequenced With Cemiplimab in Advanced NSCLC. ClinicalTrials.gov. Updated May 13, 2026. Accessed July 8, 2026. https://clinicaltrials.gov/study/NCT05208944

3. MAIA Biotechnology Receives FDA Clearance to Open U.S. Enrollment in Ongoing Phase 2 THIO-101 Trial Expansion. News release. MAIA Biotechnology. June 3, 2026. Accessed July 8, 2026. https://tinyurl.com/5n92f94j

4. MAIA Biotechnology Receives FDA’s Fast Track Designation for Ateganosine as a Treatment for Non-Small Cell Lung Cancer. News release. MAIA Biotechnology. July 28, 2025. Accessed July 8, 2026. https://tinyurl.com/58nzpra5