A Phase II Study of the MEK 1/2 Inhibitor AZD6244 (Selumetinib, ARRY-142866) in Relapsed or Refractory Multiple Myeloma
Authors: Holkova Beata , Badros Ashraf Z. , Geller Robert , Voorhees Peter M. , Zingone Adriana , Korde Neha , Lin Hui-Yi , Tombes Mary Beth , Shrader Ellen , Sankala Heidi , Kmieciak Maciej , Roberts John D. , Sullivan Daniel , Landgren Ola , Grant Steven 
Published: October 2019

Abstract
Abstract 2931
AZD6244 is a potent, selective, oral, non-ATP competitive small molecule inhibitor of the mitogen-activated protein kinase, MEK 1/2 that has shown significant pre-clinical activity in multiple myeloma (MM) cells, both in vitro and in vivo, as well as a favorable clinical profile. The present phase II study was designed to determine the response rate for AZD6244 in patients with relapsed or refractory MM.
The study utilized a two-stage Simon design to allow for early termination if there was strong evidence of regimen inactivity. Eligible patients were restricted to those with MM who have had at least 2 prior regimens. AZD6244 capsules (75 mg) were administered orally twice daily continuously for 28 day cycles. Response was evaluated after 3 cycles.
To date, 37 patients have been enrolled (13 in the 1st stage and 24 in the 2nd stage). One subject enrolled in the 1st stage was not treated. Gender enrollment was balanced (male/female 18/19). The median age of treated patients was 65 years [range 43–81]. ECOG performance scores ranged from 0–2. The median number of prior therapies was 5 [range 2–11].
The most common treatment-related adverse events (occurring in 10–50% of patients) were leukopenia, acneiform rash and other skin/subcutaneous tissue manifestations, fatigue, limb edema, increased aspartate aminotransferase (AST), neutropenia, nausea, facial edema, vomiting, thrombocytopenia, increased creatine phosphokinase, and diarrhea. The most common grade 3 and 4 toxicities (CTCAE v4) included fatigue, peripheral sensory neuropathy, increased AST, neutropenia, nausea, hypotension, thrombocytopenia, increased alanine aminotransferase, and diarrhea. Five deaths have occurred: 2 associated with sepsis, 1 associated with acute kidney injury, all deemed possibly related to AZD6244; and 2 due to disease progression after discontinuation of study treatment.
Two objective partial responses have been reported, the first of which justified expansion of the study to the 2nd stage. Twelve patients have had a best response of stable disease, 11 patients have had progressive disease, 1 patient withdrew after cycle 1 (unrelated to toxicity) and did not have response assessed, 3 patients died before response was assessed, and 7 patients are too early to evaluate. Accrual is ongoing to determine if the response threshold in the 2nd stage can be met.
Correlative studies are ongoing and are designed to identify potential mechanisms of response/resistance to AZD6244, and to determine the effect of AZD6244 on the bone marrow microenvironment. These include, among others, assessment of pre- and post-treatment expression of phospho-MEK 1/2 and -ERK 1/2, and total levels of Bim. Fifteen patients consented to correlative sampling of bone marrow, blood and/or urine. Results and sample analysis are pending.
It is concluded that AZD6244 has modest activity as a single agent in relapsed or refractory MM. This trial also provides a foundation for successor studies employing the MEK 1/2 inhibitor AZD6244 in combination with other agents in patients with MM.

Disclosures:
Voorhees: Pfizer: Research Funding; Centocor Ortho Biotech: Research Funding; Celgene: Research Funding; MedImmune: Consultancy; Merck: Research Funding.