Heidelberg Pharma AG announced that the clinical Phase I/IIa study with the lead development candidate HDP-101 has already started to recruit patients for the fifth patient cohort with a dosing of 100 µg/kg. The Safety Review Committee's (SRC) evaluation of patient data concluded that no dose-limiting toxicities have occurred to date. The first four dose levels have shown to be safe and well tolerated.

So far 12 patients have been treated in the trial. With the expansion of study sites this summer, patient enrollment has significantly accelerated. One patient from the third cohort has now been on HDP-101 monotherapy for over nine months and has been treated with eleven doses.

The BCMA antibody Amanitin conjugate HDP-101 is being tested in an open-label, multicenter study for the treatment of relapsed or refractory multiple myeloma, a cancer of the bone marrow. The first part of the study is a Phase I dose escalation study to determine the maximum tolerated dose of HDP-101. These findings will be used to determine the dose for the Phase IIa part, the primary objective of which is to initially evaluate the anti-tumor activity of HDP-101.

The open-label, multicenter Phase I/IIa trial is expected to enroll up to 36 patients in the first part and up to 30 patients in the second part. Patients in Phase IIa will be stratified based on 17p deletion status. Preclinical data show that Amanitin has the potential to work particularly well on those tumors that have been genetically altered by a so-called 17p deletion to bypass a particular protective mechanism of cells.

Patients with such a deletion generally respond less well to standard therapies and have a significantly poorer prognosis. Phase IIa will not only validate the efficacy of HDP-101 in patients with multiple myeloma, but also the clinical relevance of the 17p deletion.