Preliminary Evidence Of Anti Tumor Activity Of Selinexor (KPT-330) In a Phase I Trial Ofa First-In-Class Oral Selective Inhibitor Of Nuclear Export (SINE) In Patients (pts) With Relapsed / Refractory Non Hodgkin’s Lymphoma (NHL) and Chronic Lymphocytic Leukemia (CLL)
Authors: Kuruvilla John , Gutierrez Martin , Shah Bijal D. , Gabrail Nashat Y. , de Nully Brown Peter , Stone Richard M. , Garzon Ramiro , Savona Michael , Siegel David S. , Baz Rachid , Mau-Sorensen Morten , Davids Matthew S. , Byrd John C. , Shacham Sharon , Rashal Tami , Yau Cindy YF , McCauley Dilara , Saint-Martin Jean-Richard , McCartney John , Landesman Yosef , Klebanov Boris , Pond Greg , Oza Amit M. , Kauffman Michael , Mirza Mansoor R 
Published: October 2019

Abstract

Background
Exportin 1 (CRM1/XPO1) is the exclusive transporter of the majority of Tumor Suppressor Proteins (TSP) out of the nucleus, rendering these TSPs non-functional. Selinexor (KPT-330) is a potent, oral SINE XPO1 antagonist, forcing the nuclear retention and activation of >10 TSPs resulting in NHL and CLL cell death in vitro, while sparing normal lymphocytes and other hematopoietic cells. Oral Selinexor has marked activity in murine models of NHL and CLL including R-CHOP resistant tumors. Dogs with spontaneous B- and T-cell lymphomas exposed to the related SINE Verdinexor demonstrate potent anti tumor effect and good tolerability.

Methods
Patients (pts) with advanced NHL or CLL relapsed/refractory to all available drug classes were dosed with oral Selinexor (8-10 doses / 4-week cycle) as part of a Phase 1 trial in hematological malignancies (NCT01607892). Detailed pharmacokinetic (PK) and pharmacodynamic (PDn) analyses and serial tumor biopsies were obtained. Response evaluation was performed every cycle.

Results
18NHL/CLL pts with median age 66.5yrs; ECOG PS 0/1: 8/10; median number of prior regimens: 4.5 [range 2-11], received KPT-330 across 6 dose levels (3 to 30 mg/m2). Ten pts experienced drug-related grade 3/4 Adverse Events (AEs) including thrombocytopenia without bleeding (n=6), neutropenia (n=5), dehydration (n=1), syncope (n=1), hypotension (n=1), fatigue (n=1). The most common grade 1/2 toxicities were: anorexia (10/18pts; 56%), fatigue (9/18; 50%), diarrhea (6/18; 33%), vomiting (6/18; 33%), neutropenia (5/18; 28%), malaise (3/18; 17%), anemia (3/18; 17%) and weight loss (3/18; 17%). These adverse events were manageable with supportive care. 23mg/m2, one case of Grade 4 thrombocytopenia for >5 days without bleeding was reported as a DLT for the cohort; this patient with refractory follicular NHL was continued on therapy at the same dose and schedule with intermittent platelet support with SD for 83 days on study.Dose escalation continues.There were no clinically significant cumulative toxicities or major organ dysfunction and pts have remained on therapy for ≥6 cycles. Maximum tolerated dose has not been reached; dosing at 35 mg/m2 twice weekly is ongoing.PK analysis at doses of 3-35 mg/m2demonstrated a dose proportional increase in Cmax and AUC with increasing dose. Elimination half-life was independent of dose and ranged from 4.7-7.0 hours. Significant increases (2-20x) in total leukocyte XPO1 mRNA levels (PDn marker) were observed at all doses, with higher doses demonstrating higher levels of XPO1 mRNA induction.Evaluation of lymph node biopsies from 2 pts confirms Selinexor-induced nuclear localization of multiple TSPs as well as apoptosis of tumor cells. Response was evaluable in 15pts; Selinexor treatment induced tumor shrinkage or disease stabilization in 80%(n=12) of pts with relapsed/refractory NHL/CLL who had progressive disease on study entry (Figure 1). 20% (n=3) of pts had clinical progression. One patient with ibrutinib-refractory CLL with Richter's transformation who progressed on chemotherapy achieved a rapid 60% reduction in lymph nodes in Cycle 1 and was referred for transplantation. A patient with DLBCL refractory to R-CHOP and bone marrow transplantation achieved a near CR (93% tumor shrinkage) and remains on study >11 months.

Conclusions
Oral Selinexor is generally well tolerated, with favorable PK andPDn parameters. In this cohort of heavily pretreated, refractory/refractoryNHLand CLL with progressive disease on study entry, single agent oral Selinexor induced tumor shrinkage in the majority of pts.

Disclosures:
Kuruvilla: Seattle Genetics: Consultancy, Honoraria, Research Funding; Hoffman LaRoche: Consultancy, Honoraria, Research Funding; Janssen: Honoraria; Celgene: Consultancy, Honoraria; Lundbeck: Consultancy, Honoraria; Karyopharm: Research Funding. Shah:Seattle Genetics, Inc.: Research Funding; NCCN: Membership on an entity’s Board of Directors or advisory committees; SWOG: Membership on an entity’s Board of Directors or advisory committees; Celgene: Speakers Bureau; Janssen/Pharmacyclics: Speakers Bureau. Garzon:Karyopharm: Research Funding. Siegel:Celgene, Millennium, Onyx: Honoraria, Speakers Bureau. Baz:Sanofi: Research Funding; Karyopharm: Research Funding; Novartis: Research Funding; Bristol Myers Squibb: Research Funding; Millenium: Research Funding; Celgene: Research Funding. Shacham:Karyopharm Therapeutics Inc.: Employment, Equity Ownership, Membership on an entity’s Board of Directors or advisory committees, Patents & Royalties. Rashal:Karyopharm Therapeutics: Employment, Equity Ownership. Yau:NPM Pharma Inc: NPM Pharma hired Ozmosis Research as CRO for this trial Other. McCauley:Karyopharm Therapeutics: Employment, Equity Ownership, Patents & Royalties. Saint-Martin:Karyopharm Therapeutics: Employment, Equity Ownership. McCartney:Karyopharm Therapeutics: Employment, Equity Ownership. Landesman:Karyopharm Therapeutics: Employment. Klebanov:Karyopharm Therapeutics: Employment. Pond:Ozmosis Research: Consultancy. Kauffman:Karyopharm Therapeutics Inc.: Employment, Equity Ownership, Membership on an entity’s Board of Directors or advisory committees. Mirza:Karyopharm Therapeutics: Consultancy, Equity Ownership, Membership on an entity’s Board of Directors or advisory committees.