A Phase 1 study of BAL101553, a novel tumor checkpoint controller targeting microtubules, administered as 48-h infusion in adult patients with advanced solid tumors.

Purpose BAL101553, the prodrug of the microtubule-destabilizer BAL27862, previously showed signs of antitumor activity when administered as a 2-h infusion, but its use was limited by vascular toxicity. We investigated an alternative dosing strategy aimed at improving the safety profile of BAL101553. Methods This multicenter, open-label, Phase 1 dose-escalation study used a 3 + 3 design to determine the maximum tolerated dose (MTD), dose-limiting toxicities (DLTs), pharmacokinetics, and antitumor activity of BAL101553 administered as a 48-h IV infusion on Days 1, 8, and 15 of a 28-day cycle. Patients received oral BAL101553 on Days 15-21 of cycle 2 to assess oral bioavailability. Results BAL101553 was well tolerated at doses up to ≤70 mg/m2. Three grade 3 DLTs occurred: hypotension (70 mg/m2), hyponatremia and neutropenia (both 90 mg/m2). The MTD for 48-h IV BAL101553 was 70 mg/m2. At this dose level, the AUC for BAL27862 was 8580 ng.h/mL and the Cmax was 144 ng/mL. No apparent dose-related effects on blood pressure were observed with 48-h BAL101553 IV infusion. BAL27862 oral bioavailability was >80%. Conclusions Continuous 48-h IV BAL101553 infusion achieved higher exposure of the BAL27862 active metabolite than a 2-h infusion at the RP2D and did not cause vascular toxicity. Clinicaltrials.gov registration: NCT02895360.

DNA damage-induced transcriptional program in CLL: biological and diagnostic implications for functional p53 testing.

The DNA damage pathway plays a central role in chemoresistance in chronic lymphocytic leukemia (CLL), as indicated by the prognostic impact of TP53 and ATM loss/mutations. We investigated the function of the p53 axis in primary CLL samples by studying p53 and p21 responses to irradiation by FACS and RT-PCR. We observed a distinct response pattern for most cases with a 17p deletion (n = 16) or a sole TP53 mutation (n = 8), but not all cases with a p53 aberration were detected based on a number of different assays used. Samples with a small clone with a TP53 mutation remained undetected in all assays. Only 1 of 123 cases showed high expression of p53, which is suggestive of p53 aberration without proof of mutation of TP53. Samples with an 11q deletion showed a heterogeneous response, with only 13 of 30 showing an abnormal response based on cutoff. Nevertheless, the overall induction of p53 and p21 was impaired, suggesting a gene-dosage effect for ATM in the 11q-deleted samples. The detectability of p53 defects is influenced by clonal heterogeneity and sample purity. Functional assays of p53 defects will detect a small number of cases not detectable by FISH or TP53 mutational analysis. The clinical utility of functional p53 testing will need to be derived from clinical trials.

A novel Fc-engineered monoclonal antibody to CD37 with enhanced ADCC and high proapoptotic activity for treatment of B-cell malignancies.

The tetraspanin CD37 is widely expressed in B-cell malignancies and represents an attractive target for immunotherapy with mAbs. We have chimerized a high-affinity mouse Ab to CD37 and engineered the CH2 domain for improved binding to human Fcγ receptors. The resulting mAb 37.1 showed high intrinsic proapoptotic activity on malignant B cells accompanied by homotypic aggregation. Furthermore, the Ab-mediated high Ab-dependent cell-mediated cytotoxicity (ADCC) on lymphoma and primary CLL cells. mAb 37.1 strongly depleted normal B cells as well as spiked B-lymphoma cells in blood samples from healthy donors as well as malignant B cells in blood from CLL patients. In all assays, mAb 37.1 was superior to rituximab in terms of potency and maximal cell lysis. A single dose of mAb CD37.1 administered to human CD37-transgenic mice resulted in a reversible, dose-dependent reduction of peripheral B cells. In a Ramos mouse model of human B-cell lymphoma, administration of mAb 37.1 strongly suppressed tumor growth. Finally, a surrogate Fc-engineered Ab to macaque CD37, with in vitro proapoptotic and ADCC activities very similar to those of mAb 37.1, induced dose-dependent, reversible B-cell depletion in cynomolgus monkeys. In conclusion, the remarkable preclinical pharmacodynamic and antitumor effects of mAb 37.1 warrant clinical development for B-cell malignancies.