A phase I clinical trial of AZD1775 in combination with neoadjuvant weekly cisplatin and docetaxel in borderline resectable head and neck squamous cell carcinoma (HNSCC).

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6034 Background: The WEE1 tyrosine kinase regulates G2/M transition and maintains genomic stability. In TP53-deficient tumors (via mutation or HPV inactivation), inhibiting WEE1 with AZD1775 can lead to unrestrained mitosis and cell death. We conducted a Phase I clinical trial of AZD1775 in combination with chemotherapy to define the toxicity profile, establish the maximal tolerated dose (MTD) and assess preliminary efficacy in borderline resectable HNSCC. Methods: Stage III/IVB HNSCC deemed borderline resectable by a multidisciplinary team were enrolled in a phase 1, 3 + 3 design to evaluate escalating doses of AZD1775 starting at 125 mg PO BID x 2.5 days alone as lead-in and in combination with cisplatin (25mg/m2) and docetaxel (35 mg/m2) for three additional weeks. Tumors were sequenced with UWOncoPlex (262 cancer genes); HPV status assessed via p16 IHC; toxicities graded with CTCAE v. 4.04; responses measured via RECIST 1.1 and through pathologic assessment when available. Trial is open but primary endpoints were met. Results: Eleven patients were screened; 10 enrolled and were evaluable for toxicities. The most common Grade ≥ 2 toxicities were diarrhea (4), fatigue (4), neutropenia (3) and nausea (3). The drug-limiting toxicity was Grade 3 diarrhea (2). The MTD was established at 150mg PO BID x 2.5 days, alone and in combination with neoadjuvant cisplatin and docetaxel. Two patients were HPV+/TP53wt, 1 was HPV+/ TP53 mut; 6 were TP53mut/HPV-; 1 was TP53 wt/HPV-. Seven out 10 patients had a response. Two patients dropped out after the first week with AZD1775, one due to an allergic reaction to docetaxel and another due to non-compliance. Eight completed neoadjuvant therapy and 7 of those converted to surgery: 2 had pathologic CRs (both HPV+/TP53wt); 4 had PR (all TP53 mutants); 1 (TP53wt/HPV-) had a PR by RECIST, but SD by pathology and 1 had PD. Conclusions: AZD1775 is safe and tolerable in combination with neoadjuvant cisplatin and docetaxel. Results show this combination to have promising anti-tumor efficacy in borderline resectable HNSCC with TP53 deficiency, and merits further investigation with the established MTD as the recommended Phase II dose. Clinical trial information: NCT02508246.