In continuation of my update on bosutinib
Four-year results for an ongoing study of second-line bosutinib indicate that the tyrosine kinase inhibitor (TKI) offers long-term efficacy with manageable side effects for patients with chronic phase chronic myeloid leukaemia (CP CML).
“Overall, these findings highlight the therapeutic potential of bosutinib as second-line therapy in IM-R [imatinib resistant] or IM-I [imatinib intolerant] CP CML patients”, say Tim Brümmendorf (Universitätsklinikum der RWTH Aachen, Germany) and co-investigators.
In the phase I/II trial, bosutinib 500 mg/day was given for a median of 24.8 months to 196 IM-R and 90 IM-I patients; 59% of 264 evaluable patients achieved or maintained a major cytogenetic response (MCyR) for at least 4 weeks, including 59% of the IM-R and 61% of the IM-I groups.
Of the 248 patients without a complete cytogenetic response (CCyR) at baseline, 57% achieved a MCyR and 47% a CCyR during bosutinib therapy. And 14 of the 16 patients with a baseline CCyR maintained this response for between 12 and 288 weeks; two discontinued bosutinib because of adverse events (AEs) and were not reassessed.
The median times to MCyR and CCyR were 12.3 and 24.0 weeks, respectively.
The 4-year cumulative incidences of MCyR and CCyR, at 59% and 49%, respectively, were similar to the previously reported 2-year figures of 59% and 48%, prompting the authors to suggest that “most initial responses occur within 2 years from bosutinib treatment initiation.”
The rate of cumulative progression or death during treatment was an estimated 19% at 4 years.
The Kaplan–Meier-estimated probability of maintaining MCyR at 4 years was found to be high for the whole population and the IM-R and IM-I groups, at 74.5%, 69.3% and 86.3%, respectively, and the median duration of this response had not yet been reached.