Abstract CT113: A Phase I study of Suberoylanilide Hydroxamic Acid (SAHA) with Temsirolimus in children with newly diagnosed or progressive diffuse intrinsic pontine glioma (DIPG)

Background/rationale: Diffuse intrinsic pontine glioma (DIPG) in children remains essentially incurable with a median survival of 12 months. Radiation therapy is currently the standard treatment modality. To date chemotherapy or biologic agents have had no meaningful increase in survival, making it imperative to profile novel therapeutic combinations. Data from biopsied DIPG showed the PI3K/AKT/mTOR pathway as a major oncogenic player. At the gene level high PDGFR amplification (most commonly seen) and overexpression of the PI3K-Akt-mTOR pathway were noted in these tumors. Focal amplifications of genes within the receptor tyrosine kinase-Ras-phosphoinositol 3-kinase signaling pathway were found in 47% of DIPG. Thus targeting this pathways with mTOR inhibitors could hold therapeutic promise. Elevated expression of DNA repair proteins in the NHEJ and HRR pathway are known to induce resistance to radiation. Preclinical data shows inhibition of these pathways potentiates the sensitivity of these tumors to radiation. SAHA a pan HDAC inhibitor, has been associated with decreased expression of key DNA repair proteins in both the NHEJ and HRR pathways. Both temsirolimus (an mTOR inhibitor) and SAHA are well described in pediatric clinical trials with an established maximum tolerated dose (MTD). The efficacy of the combination of temsirolimus and SAHA has been well-established in other malignancies including prostate cancer, mantle lymphoma, and renal carcinoma. This is the first multi-targeted therapeutic trial in pediatric DIPG, using SAHA and temsirolimus in a combinatorial approach, targeting the key oncogenic pathway and molecules along with enhancing the radiation sensitivity. Correlative study: Stratum I (chemoradiotherapy phase): Histone acetylation will be quantified from peripheral blood mononuclear cell (PBMC) collected prior to the first dose of vorinostat and radiation and at the end of radiation. Stratum I and II (maintenance phase): Evaluation of histone acetylation, phosphorylated 70S6K and Akt on day 1 and 8 (prior to chemotherapy with temsirolimus) during cycle 1 and cycle 2. Methods Patients with a performance score of 50 or greater with newly diagnosed (Stratum 1) or progressive DIPG (stratum II) as confirmed by gadolinium enhanced MRI are eligible. Biopsy is not mandatory. Stratum I: Patients will receive radiation therapy concurrently with vorinostat on the days of radiation at a dose of 230mg/m2/dose, followed by adjuvant therapy with vorinostat and temsirolimus for 10 cycles if patients do not have progressive disease. Stratum II: Patients will receive vorinostat and temsirolimus for 12 cycles (28 day cycle), if patient does not have progressive disease. SAHA will be given once daily at 230 mg/m2 orally from day 1 to day 8, along with temsirolimus at 25mg/m2 intravenously on day 1 and day 8. This will be the dose level 1 and 2 dose escalations and 1 dose de-escalation will be allowed. A standard 3+3 design will be used and a minimum of 9 patients and a maximum of 18 patients will be enrolled. Trial is ongoing (30% of planned patients enrolled), with patients now in the second dose level (enrollment of this cohort started on September 2018). No dose limiting toxicity (DLT) were noted at the first dose level. Trial: NCT02420613 (currently recruiting). Note: This abstract was not presented at the meeting. Citation Format: Soumen Khatua, Joya Chandra, Miriam M. Morrell, Heather B. Meador, David I. Sandberg, Jeffrey Weinberg, Greg Fuller, Leena Ketonen, Jason M. Johnson, Kenneth R. Hess, Wafik Zaky. A Phase I study of Suberoylanilide Hydroxamic Acid (SAHA) with Temsirolimus in children with newly diagnosed or progressive diffuse intrinsic pontine glioma (DIPG) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr CT113.