Effect of bexarotene on platelet counts in patients undergoing cancer treatment: An analysis of clinical trials in lung cancer and leukemia

Abstract

e20533 Background: Bexarotene (Bex) is an oral retinoid X receptor agonist with activity against cutaneous T cell lymphoma and currently under investigation for other malignancies. In patients receiving this agent for acute myeloid leukemia (AML), we noted increases in platelet counts. We therefore reviewed the available clinical trial data on Bex and its effects on platelet counts. Methods: We analyzed platelet count data from 3 Bex clinical trials encompassing non-small cell lung cancer (NSCLC) and AML. Results: In two phase III trials of Bex in NSCLC, patients underwent carboplatin + paclitaxel (CarP, n=587) or cisplatin + vinorelbine (CisV, n=613) and were randomized to receive concurrent Bex or placebo. More patients on Bex than on placebo had an increase in platelet count of at least 50 K/uL (55% vs. 27% for CarP, p<0.0001; 81% vs. 66% for CisV, p<0.0001) over pre-treatment baseline. The median increase in platelet count was higher on Bex than on placebo (69 vs 0 K/uL for CarP, p<0.0001; 168 vs. 95 K/uL for CisV, p<0.0001) and was maintained while on treatment. In both NSCLC trials, the median time to platelet increase >50 K/uL on Bex was 22 days. Similar findings were seen in a phase I monotherapy trial in AML where 5/18 (28%) patients achieved platelet transfusion independence with peak platelet counts of 40–91 K/uL. Conclusions: Clinically significant increases in platelet counts were seen in all 3 clinical trials examined. These data suggest that Bex improves platelet counts in patients with a variety of cancer types, both as monotherapy and with concurrent chemotherapy. Its effect on megakaryopoiesis and its potential role as a supportive care measure should be further evaluated. [Table: see text]