Treatment Guided By Next Generation Functional Drug Screening Provides Clinical Benefit in Advanced Aggressive Hematological Malignancies: Final Evaluation of the Open Label, Single Arm Exalt Trial

Background: Aggressive hematological malignancies in relapsed/refractory setting bear a dire prognosis with low cure rates and short survival. Matching these patients to therapies is challenged by complexity due to spatial and temporal tumor evolution and incomplete understanding of genotype to phenotype correlations. Direct functional testing could address these impediments. The EXALT trial is an interventional, one-arm study designed to assess the clinical value of next generation functional drug screening (ngFDS). An interim analysis on 17 patients suggested a clinical benefit (Snijder et al., Lancet Hematol. 2017). Methods: We applied image-based ngFDS to quantify differential ex-vivo sensitivity of primary patient tumor cells to respective non-tumor cells towards 136 small molecule drugs, including EMA approved for any indication or experimental. We screened bone marrow, peripheral blood or lymph node material from 143 patients who suffered from late stage aggressive hematological malignancies (acute leukemias, aggressive B- and T-cell lymphomas) , discussed the results in a multidisciplinary tumor board and recommended treatments to physicians (A). The primary endpoint of this study was the percentage of patients reaching a PFS-ratio (PFS(ngFDS treatment)/PFS(previous treatment)) of ≥1.3 with an H0 hypothesis < 15% patients. The secondary endpoint was overall response rate (ORR) defined as proportion of patients reaching complete remission (CR) or partial remission (PR). Additionally, we performed a post hoc analysis to evaluate the matching of ngFDS to drugs used in actual treatment (matching score of received treatment). Results: 56 (39%) patients were evaluable and treated according to ngFDS based recommendations. With 30 of 56 (54%) ngFDS guided patients experiencing a PFS ratio of ≥1.3, the primary study endpoint was reached. 11 patients (37%) had ongoing response at censoring date (B). The median follow-up was 718 days. The median number of days from sampling to treatment was 21 (range 4-77). The ngFDS treatment regimens consisted of a median of 2 drugs (range: 1-6). ORR was 55% for all evaluable ngFDS treated patients, 60% for the lymphoid subgroup and 41% for the myeloid subgroup. Patients on ngFDS guided treatment with performance status ECOG ≤ 1 had a median PFS of 207 days compared to a median PFS of 29 days for patients with higher ECOG (p < 0.001, C). 24 of 39 (62%) patients with ECOG ≤ 1 had a PFS ratio of ≥1.3 (D). In disease specific