A Diabetes Drug Shows an Early Signal Against Chemotherapy Resistance in Pancreatic Cancer

A diabetes medicine may have helped standard chemotherapy work against advanced pancreatic cancer in a small phase 2 study. In the single-center SITGEM-CARE trial, 22 patients received sitagliptin alongside gemcitabine and nab-paclitaxel. The response signal is encouraging, but the trial had no control group and cannot show that sitagliptin produced the apparent improvement.

Key Number: The objective response rate was 36.4%, but its 95% confidence interval stretched from 17.2% to 59.3%, showing how uncertain a 22-patient estimate remains.

A repurposed drug added to established chemotherapy

Sitagliptin is widely used to lower blood glucose in type 2 diabetes by inhibiting the enzyme DPP-4. The researchers did not begin with its usual metabolic role. They used structure-based computational screening to look for approved drugs that might interfere with RRM1 and RRM2, the two subunits of ribonucleotide reductase. This enzyme helps cells produce the DNA building blocks needed for replication and has been linked to resistance to gemcitabine.

The resulting trial enrolled adults with locally advanced or metastatic pancreatic ductal adenocarcinoma and good performance status. Participants took 100 milligrams of sitagliptin daily and received gemcitabine plus nab-paclitaxel on days one and eight of each 21-day cycle. Thirty people consented, but only 22 started treatment and entered the efficacy and safety analyses.

What the trial observed

Eight patients had a confirmed partial response, 11 had stable disease and three had progressive disease. That produced an objective response rate of 36.4% and a disease-control rate of 86.4%. Median progression-free survival was 6.6 months. Median overall survival was estimated at 12.5 months, although median follow-up was only 9.9 months and the upper confidence limit had not been reached.

No grade 4 or 5 treatment-related adverse events were reported. The investigators said no participant discontinued the study drug because of treatment-related toxicity. Those findings support further testing, but a cohort this small is poorly suited to detect uncommon harms.

For context, the randomized MPACT trial that established gemcitabine plus nab-paclitaxel as a standard option reported a 23% independently assessed response rate and median overall survival of 8.5 months. SITGEM-CARE used a different schedule, mixed locally advanced and metastatic disease, and enrolled a far smaller population at one Chinese center. Its results therefore cannot be compared as if the two trials were treatment arms in the same experiment.

How sitagliptin might change resistance

In pancreatic-cancer cell lines, patient-derived organoids and mouse models, the team found that sitagliptin reduced RRM1 and RRM2 protein levels and restored sensitivity to gemcitabine. Genetic experiments supported a functional role for this pathway. The researchers also reported stronger activity when sitagliptin was combined with chemotherapy in several preclinical models.

The precise mechanism is not settled. The paper does not show whether sitagliptin binds the ribonucleotide-reductase complex directly, changes gene activity or affects protein stability. Because sitagliptin also alters DPP-4 biology, metabolic, immune or tumor-environment effects could contribute. The clinical trial did not collect tumor tissue for pharmacodynamic testing, so it could not confirm that RRM1 or RRM2 changed inside patients' tumors.

What happens next

The important next step is a larger, multicenter randomized trial comparing the chemotherapy backbone with and without sitagliptin. Such a study would need stratification by disease stage, longer follow-up and direct measurements showing whether the proposed resistance pathway changes in tumors. Until then, drug repurposing has produced a plausible and testable hypothesis, not a proven pancreatic-cancer therapy.