Increasing Anti-Cancer Efficacy of Radiotherapy
As cancer cells have been observed to be more susceptible than normal cells to increased levels of hydrogen peroxide, we believe the conversion of excess superoxide to hydrogen peroxide by our dismutase mimetics has the potential to increase the anti-cancer efficacy of radiotherapy. We are evaluating our dismutase mimetics to determine their ability to increase the anti-cancer efficacy of high daily doses of radiotherapy, which we have demonstrated in our pre-clinical studies. This increased efficacy could be particularly important in settings where the current anti-cancer efficacy of radiotherapy alone is insufficient to achieve the desired outcome.
In our pre-clinical studies, we have observed increased anti-cancer efficacy of higher daily doses of radiotherapy in combination with our dismutase mimetics.
Additional pre-clinical studies have provided further evidence supporting our dismutase mimetics’ biological mechanism in combination with radiotherapy in solid tumors. To test the hypothesis that our dismutase mimetics’ conversion of superoxide to hydrogen peroxide increases the anti-cancer efficacy of radiotherapy, we genetically engineered NSCLC tumors to overexpress catalase enzyme when triggered. This overexpression of catalase, a native enzyme that rapidly removes hydrogen peroxide, blocked the dismutase mimetic’s synergy with radiotherapy in an experiment similar to the ones described above.
Clinically, SBRT is increasingly used in patients with certain tumors, such as those seen in locally advanced pancreatic cancer (LAPC) and non-small cell lung cancer (NSCLC) that are less responsive to the small daily doses typical of IMRT. SBRT typically involves a patient receiving three to five large doses of radiotherapy, in contrast to the 30 to 35 small daily doses typical of IMRT. Even with the use of SBRT, the opportunity for improvement in treatment outcomes is substantial.
To explore this opportunity, we are currently conducting a pilot, randomized, placebo-controlled Phase 1b/2a trial of GC4419 in combination with SBRT in patients with LAPC whose tumor cannot be resected. The primary objective of this trial is to determine the maximum tolerated daily dose of SBRT in conjunction with our dismutase mimetic, with secondary measures assessing progression-free survival, objective response rate and tumor resectability compared to placebo. We believe this combination therapy may lead to improved patient survival rates, which we will also track in our clinical development.
We plan to leverage our observations from our GC4419 SBRT pilot Phase 1b/2a trial in LAPC to help develop GC4711 to increase the anti-cancer efficacy of SBRT. We have successfully completed a Phase 1 trial of intravenous GC4711 in healthy volunteers and plan to commence a Phase 1b/2a trial with GC4711 in combination with SBRT in patients with NSCLC. In addition to this GC4711 Phase 1b/2a trial in NSCLC, we plan to conduct future trials with GC4711 in combination with SBRT, including in LAPC if we are successful in our ongoing SBRT GC4419 pilot Phase 1b/2a trial in that indication. We are also currently evaluating several oral formulations of GC4711 in a Phase 1 trial in healthy volunteers, based on pre-clinical studies suggesting that GC4711 can be delivered orally.