Abstract A28: Use of a high-throughput screen of primary leukemia cells to personalize therapy for relapsed/refractory AML: Proof of concept and clinical implementation of precision medicine.

Context: For patients with relapsed/refractory AML, therapeutic success is unpredictable with current chemotherapeutic regimens. Moreover, multiple courses of therapy have resulted in co-morbid conditions which can preclude the patient from receiving a bone marrow transplant. Objective: In order to identify a successful chemotherapeutic regimen for these patients, we have developed a high-throughput assay that utilizes primary (patient-derived) leukemia cells and tested for chemo-sensitivity and resistance against a panel of FDA approved agents used to treat AML. Design: This assay was developed in 1536 well format and optimized against a panel of leukemia and lymphoma cell lines to determine optimal concentration of cells needed to achieve statistically significant reproducible results. Twelve point dose response curves were performed in duplicate for all agents. Alamar Blue reduction and Annexin V staining were used as indicators of cell viability. Results: Using this assay, we demonstrated in vitro resistance against drugs already clinically administered and importantly showed in vitro sensitivity to agents that had not been previously administered. The index patient was a 32-year-old woman with primary refractory AML who had received six different therapeutic regimens prior to testing, all of which demonstrated in vitro resistance using our assay. The blasts were sensitive, however, to 6-thioguanine with an inhibitory concentration (EC50) of 70 nanoM. Based on the in vitro data, she began a combination treatment regimen containing 6-thioguanine. Following a maintenance regimen, her circulating blast count decreased, and she had partial recovery of the neutrophil count, resulting in a dramatic decrease in the overall leukemia burden. This result was not seen with her previous therapies. After over six months of this therapy, her WBC began to rise and repeat testing indicated resistance to 6-thioguanine with EC50 > 10 microM, confirming the response seen in vivo. We have gone on to test samples from more than twenty-five patients with AML and have accurately predicted the in vivo clinical response (both sensitivity and resistance) in approximately 90% of cases. In the above case, the treatment regimen identified from the screening results is now being tested in a Phase I clinical trial for patients with relapsed/refractory AML or elderly patients unfit to receive standard AML therapy. In other cases, the treatment regimen identified from the screen provided the needed bridge to allogeneic bone marrow transplantation. Conclusions: These data demonstrate that the technology described here to pharmacologically screen drug therapy for patients with relapsed/refractory AML is both clinically useful and has a role in designing individualized treatment regimens for these patients. Citation Format: David Shum, Mark Heaney, Renier Brentjens, Peter Maslak, Joseph Jurcic, Hakim Djaballah, Mark G. Frattini. Use of a high-throughput screen of primary leukemia cells to personalize therapy for relapsed/refractory AML: Proof of concept and clinical implementation of precision medicine. [abstract]. In: Proceedings of the AACR Special Conference on Hematologic Malignancies: Translating Discoveries to Novel Therapies; Sep 20-23, 2014; Philadelphia, PA. Philadelphia (PA): AACR; Clin Cancer Res 2015;21(17 Suppl):Abstract nr A28.