Researchers at Scripps Research have identified a combination therapy strategy that kills cancer cells by attacking two of their survival mechanisms simultaneously [1].

The approach targets tumors that have lost their primary DNA repair pathways — a common feature of aggressive cancers, including many breast, ovarian, and prostate tumors. These cancers rely on backup repair systems to survive. The Scripps team found that hitting both backup systems at once leaves the cells with nowhere to turn.

The first target is ATR, a kinase enzyme that acts as a DNA damage checkpoint. ATR inhibitors are already in clinical trials and have shown modest results as standalone drugs. The second target is Pol theta, the error-prone enzyme that stitches broken DNA back together when all other repair options fail. Blocking Pol theta alone slows tumor growth. Blocking it alongside ATR is lethal to the cancer cells.

The study, published in Molecular Cell, demonstrated the combination's effectiveness in cell lines and animal models. Cancer cells treated with both inhibitors showed catastrophic accumulation of DNA damage with no viable repair pathway remaining. Healthy cells, which retain their primary repair mechanisms, were largely unaffected.

The clinical implications are significant but distant. No Pol theta inhibitor has entered human trials. Developing one will require years of medicinal chemistry, toxicology testing, and phased clinical studies. ATR inhibitors are further along but have not yet received FDA approval for any indication.

What the research provides is a clear mechanistic rationale — a blueprint that tells drug developers exactly which two targets to hit and why the combination should work. That clarity accelerates the path from bench to bedside, even if the journey remains long.

-- NORA WHITFIELD, Chicago