Background: The link between taxane resistance and activation of PI3K/AKT/mTOR signaling suggests that by inhibiting this pathway in combination with anti-microtubule agents like paclitaxel may improve treatment outcomes in many malignancies. To investigate this further we combined the TORC 1/2 inhibitor sapanisertib (TAK-228), the PI3Kα isoform inhibitor serabelisib (TAK-117), and paclitaxel in a phase I trial to determine the safety, efficacy, and RP2D. Methods: Open label, cohort study using a traditional 3+3 dose escalation design with a maximum of 5 dosing cohorts. A dose expansion of cohort 4, the recommended RP2D, is planned for February 2020. Results: Enrollment to the DLT evaluation has been completed and the clinical results are summarized in Table. Sixteen patients have been enrolled; a majority were heavily pretreated and resistant to paclitaxel. Overall, the combination was safe and tolerable. One DLT occurred due to renal dysfunction in cohort 5. 360 adverse events have been reported, but only 28 (8%) grade 3 or 4 events. The most common events were leukopenia and non-febrile neutropenia. Two patients required dose reductions as a result of pneumonitis. The ORR is currently 46% in 13 evaluable patients. CBR is 69% and PFS is currently at 10 months. Two patients achieved a CR and three patients remain on treatment. Conclusions: The combination proved to be well tolerated in the doses and schedules used in cohorts 1-4 and exhibited very promising clinical activity in heavily pretreated patients. This regimen could prove to be a highly effective treatment option and a phase 2 study is warranted at the RP2D. Clinical trial information: NCT03154294.

* Received Prior Everolimus/Temsirolimus