Anaplastic lymphoma kinase (ALK) is a receptor tyrosine kinase responsible for the development of different tumor types. Despite the remarkable clinical activity of crizotinib (Xalkori), the first ALK inhibitor approved in 2011, the emergence of resistance mutations and of brain metastases frequently causes relapse in patients. Within our ALK drug discovery program, we identified compound 1, a novel 3-aminoindazole active on ALK in biochemical and in cellular assays. Its optimization led to compound 2 (entrectinib), a potent orally available ALK inhibitor active on ALK-dependent cell lines, efficiently penetrant the blood-brain barrier (BBB) in different animal species and highly efficacious in in vivo xenograft models. Moreover, entrectinib resulted to be strictly potent on the closely related tyrosine kinases ROS1 and TRKs recently found constitutively activated in several tumor types. Entrectinib is currently undergoing phase I/II clinical trial for the treatment of patients affected by ALK-, ROS1-, and TRK-positive tumors.

The discovery of a novel class of inhibitors of cyclin dependent kinases (CDKs) is described. Starting from compound 1, showing good potency as inhibitor of CDKs but being poorly selective against a panel of serine-threonine and tyrosine kinases, new analogues were synthesized. Enhancement in selectivity, antiproliferative activity against A2780 human ovarian carcinoma cells, and optimization of the physical properties and pharmacokinetic profile led to the identification of highly potent and orally available compounds. Compound 28 (PHA-848125), which in the preclinical xenograft A2780 human ovarian carcinoma model showed good efficacy and was well tolerated upon repeated daily treatments, was identified as a drug candidate for further development. Compound 28 is currently undergoing phase I and phase II clinical trials.

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