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Another huge milestone was achieved this month by MedSIR! The PARSIFAL study finalized the enrollment of its 464 patients in 9 countries in just over 2 years. An amazing feat! It’s really not often that a trial accrues ahead of its planned rates. The patient-friendly design definitely played a huge part in this success, with all patients receiving the ground-breaking palbociclib compound regardless of the treatment arm.

The goal of PARSIFAL was to test the combination of the CDK-inhibitor, palbociclib, in combination with fulvestrant versus palbociclib in combination with letrozole in the first-line setting of patients with hormone-positive, HER2-negative metastatic breast cancer. With both arms receiving palbociclib this trial may help to determine which hormone therapy is the best partner for palbociclib. It may also determine that they are both excellent and valid options for all these patients. This would provide physicians with more flexibility at the time of choosing the optimal treatment strategy for their patients.

Robust and complete molecular studies have already been planned to be carried out on PARSIFAL patient biological samples and should help to elucidate the molecular mechanisms behind treatment efficacy and resistance as well. This information will no doubt help to better select future patients for CDK inhibitor administration and to better determine the optimal therapeutic option following palbociclib.

A big thank you from the MedSIR team to all investigators and clinical study teams, to Astra Zeneca for fulvestrant and Pfizer for palbociclib and financial support and, most of all, to all patients and their families.




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