Development of a Potent DNA Damaging Agent LP-284 for Treatment of Mantle Cell Lymphoma

Abstract

Introduction: Mantle cell lymphoma (MCL) is a rare and aggressive type of non-Hodgkin lymphoma that is characterized by the hallmark t(11;14) translocation and subsequent deregulation of expression of the Cyclin D1 (CCND1) gene. Immunochemotherapy followed by autologous stem cell transplantation and/or maintenance therapy remains the most common frontline choice for eligible individuals. Additionally, the introduction of bruton's tyrosine kinase inhibitors (BTKi), anti-CD19 chimeric antigen receptor T-cell therapy, and targeted therapies have advanced the treatment of r/r (relapsed/refractory) MCL. Unfortunately, not all patients are eligible for these therapies and durable remission is rare. Alternative therapies with novel mechanisms of action and increased efficacy are urgently needed for MCL patients. LP-284 is a novel small molecule and DNA damaging agent being developed for the treatment of MCL. The DNA lesions induced by LP-284 are repaired by transcription-coupled DNA repair and can trigger apoptosis in tumors with DNA damage repair deficiencies. As LP-284 DNA lesions block transcription, we hypothesize that LP-284 directly starves transcriptionally addicted tumors such as those with actively transcribing onco-fusion genes such as CCND1. We previously reported that LP-284 shows nanomolar potency across 6 MCL cell lines, including cells resistant to BTKi, bortezomib (Btz.), and venetoclax. Here we report LP-284's efficacy in MCL xenograft mouse models and its ability to induce ATM and subsequent gamma-H2AX phosphorylation, transcriptomic response in MCL cell lines, and preliminary toxicological profile in dogs. Methods and Results: In JEKO1-derived MCL xenograft mice, LP-284 (2 or 4 mg/kg; i.v.) was tested to evaluate its survival benefits and efficacy compared to ibrutinib (Ibr.; 50mg/kg; oral) or Btz. (1 mg/kg; i.p.). LP-284 significantly (p< 0.001; n=7 or 8 per group) increased the overall survival of these mice from 20 days in the vehicle control group to 41 days (LP-284, 2 mg/kg) and 48 days (LP-284, 4 mg/kg). Additionally, LP-284 at either concentration showed significantly increased tumor growth inhibition (TGI) compared to Ibr. or Btz. At day 17 post treatment, 113% TGI was observed in the 4 mg/kg LP-284 arm and 63% TGI was observed in the 2 mg/kg LP-284 arm, whereas Ibr. or Btz. only resulted in 8% and 22% TGI, respectively. We also tested if LP-284 (4 mg/kg) could rescue tumors that grew after treatment of Ibr. or Btz. Our data showed that LP-284 treatment resulted in near complete TGI in tumors pretreated by and grew resistant to Ibr. or Btz. No tumor regrowth nor animal death was observed 15 days after the last dose of LP-284. Additionally, we performed western blot and RNAseq on JEKO1 and REC1 cells treated by LP-284 or the vehicle for 24 hours. LP-284 treatment resulted in increased phosphorylation of ATM and gamma-H2AX in JEKO1, indicating the formation of double-strand DNA breaks. Differential gene expression analysis indicated that LP-284 reduced the expression of CCND1 by ~2 fold and there was a significant down-regulation of the MYC pathway targets. The toxicological profile of LP-284 was evaluated in a non-GLP repeat-dose toxicity study in dogs. LP-284 was administered i.v. once a day on days 1, 8, and 15 and at 0.3, 0.6, or 1.2 mg/kg/doses. Adverse effects in body weight, clinical pathology and pathology were only observed at ≥0.6 mg/kg/dose. LP-284-related changes in hematology were noted at ≥0.3 mg/kg/dose. At the microscopic level, 0.3 mg/kg/dose LP-284-related hematological changes were considered non-adverse based on the small magnitude and no associated changes in clinical hematology compared with the control animals. Therefore, under the condition of this study, the No Observed Adverse Effect Level (NOAEL) was determined to be 0.3 mg/kg/dose. Conclusions: Taken together, our results demonstrated that LP-284 has significantly increased efficacy over Ibr., Btz., and vehicle treated MCL animal models. In addition, Ibr./Btz. resistance could be overcome by LP-284. We also demonstrated that LP-284 reduced the expression of the onco-fusion gene CCND1 and the MYC pathway, which are both genes and pathways implicated in MCL. LP-284's strong potency in in vivo MCL tumor models, novel mechanism of action, and the progress in toxicological studies are in favor of further development of LP-284 as a novel MCL therapy.