Chronic myeloid leukemia (CML) is a hematological malignancy characterized by BCR-ABL1-derived permanent proliferation of myeloid progenitor cells. BCR-ABL1 tyrosine kinase inhibitors (TKI) are effective first-line therapeutic options to suppress tumor proliferation. However, TKI therapy is not always curative and drug-related side effects as well as drug resistance may evolve over time, necessitating salvage therapies.
In this case report we present a 68-year-old woman who developed second- and third-generation TKI therapy resistance with BCR-ABL1T315I and BCR-ABL1E255V mutation. Considering contraindication for hematopoietic stem cell transplantation, we treated the patient in an individual treatment attempt with a third-generation TKI ponatinib in combination with palbociclib, a CDK4/CDK6 inhibitor, which has been shown to effectively inhibit proliferation of BCR-ABL1T315I-mutated cells in vitro.
Our case study shows strong antineoplastic effects using this combination in an advanced CML patient resistant to ponatinib monotherapy as a fourth-line treatment. Combined administration of ponatinib/palbociclib at full dose showed almost a tenfold decrease (42.6 to 4.4 IS%) of BCR-ABL1-positive cells but with simultaneous hematopoietic toxicity, necessitating dose reduction.
This combination treatment showed high clinical activity. However, biological activity needs to be further characterized in prospective clinical trials.