Switch from branded to generic imatinib: impact on molecular responses and safety in chronic-phase chronic myeloid leukemia patients

Since July 2017, different generic imatinib formulations have been introduced in Italy for the treatment of patients with chronic myeloid leukemia (CML). We analyzed 168 chronic phase CML patients treated with branded imatinib for a median of 12 years (range 1–16) at a single institution who switched to a single generic formulation in order to assess the safety and impact on molecular response. The Sokal risk was low/intermediate/high in 63%, 33%, and 4% of patients, respectively. The median duration of generic imatinib treatment was 19 months (range 4–22). Twenty-seven percent of patients were in MMR and 73% were in deep molecular responses (MR4–4.5) at the time of the switch. After 12 months of treatment with generic imatinib, 140 patients were evaluable for response: 23.6% and 76.4% were respectively in MMR and in deep molecular response. When the degree of response was compared with the best molecular response observed with branded imatinib, it was found that 84% of patients maintained the response previously achieved, 6% improved it, and 10% of patients had a molecular fluctuation from the previous deep molecular response to MMR. Only 1 patient lost the MMR and no patient switched to another TKI for inefficacy. In terms of safety, 20% of patients reported new or worsening side effects, but only 2 patients returned to branded imatinib for toxicity. Our data show that the switch to generic imatinib in patients who have been previously treated with branded imatinib appears to maintain efficacy, although a proportion of patients experience new or worsening side effects.