While there has been significant previous experience in using CFC assays to evaluate the toxic effects of more traditional classes of therapeutics, little was known until recently about this assay’s utility in evaluating the newer classes of targeted therapeutics such as kinase inhibitors (KIs).
The success of Imatinib in targeting the ABL tyrosine kinase in chronic myeloid leukemia has prompted the development of a number of other KIs for the treatment of various cancers, making this drug class currently one of the most active areas in pharmaceutical development. Unfortunately myelotoxicity, in particular, neutropenia is often a major side effect of this compound class.
Using in vitro CFU-GM assays, scientists at ReachBio determined the IC50 values of six KIs (Imatinib, Lapatinib, Erlotinib, Dasatinib, Sorafenib, and Sunitinib) and compared them to the degree of clinical neutropenia caused by these drugs, as reported in the literature.
For this assay, functionally prequalified human bone marrow cell samples from three different donors were mixed with the KIs over a broad concentration range in ColonyGEL methylcellulose-based media, plated in 35 mm dishes (n=3), and the resulting CFU-GM colonies were enumerated. The range of IC50 values thus determined allowed the ranking of these compounds in terms of toxicity to the bone marrow progenitors.