Novel antitumor therapies against the PI3K-AKT-mTOR pathway are increasingly used to treat cancer, either as single agents or in combination with chemotherapy or other targeted therapies. Although these agents are not known to be myelosuppressive, an increased risk of infection has been reported with rapamycin analogs. However, the risk of infection with new inhibitors of this pathway such as PI3K, AKT, mTORC 1/2 or multi-kinase inhibitors is unknown.
Methods
In this retrospective case-control study, we determined the incidence of infection in a group of 432 patients who were treated on 15 phase I clinical trials involving PI3K-AKT-mTOR pathway inhibitors (cases) vs a group of 100 patients on 10 phase I clinical trials of single agent non-PI3K-AKT-mTOR pathway inhibitors (controls) which did not involve conventional cytotoxic agents. We also collected data from 42 patients who were treated with phase I trials of combinations of PI3K-AKT-mTOR inhibitors and MEK inhibitors and 24 patients with combinations of PI3K-AKT-mTOR inhibitors and cytotoxic chemotherapies.
Results
The incidence of all grade infection was significantly higher with all single agent PI3K-AKT-mTOR inhibitors compared to the control group (27% vs 8% respectively, OR: 4.26, 95% CI: 1.9-9.1, p=0.0001). The incidence of grade 3 and 4 infection was also significantly higher with PI3K-AKT-mTOR inhibitors compared to the control group (10.3% vs 3%, OR: 3.74, 95% CI: 1.1-12.4, p=0.02). Also the combination of PI3K-AKT-mTOR inhibitors and chemotherapy was associated with a significantly higher incidence of all grade (OR: 4.79, 95% CI: 2.0-11.2, p=0.0001) and high grade (OR: 2.87, 95% CI: 1.0-7.6, p=0.03) infection when compared with single agent PI3K-AKT-mTOR inhibitors.
Conclusion
Inhibitors of the PI3K-AKT-mTOR pathway can be associated with a higher risk of infection. Combinations of PI3K-AKT-mTOR inhibitors and cytotoxic chemotherapy significantly increase the risk of infection. This should be taken into consideration during the design and conduct of trials involving PI3K-AKT-mTOR pathway inhibitors, particularly when combined with chemotherapy or myelosuppressive agents.