Phase II trial of temsirolimus in patients with relapsed or refractory multiple myeloma

In a phase II trial, 16 patients with relapsed refractory multiple myeloma received temsirolimus 25mg I.V. weekly until progression. One partial response and 5 minor responses were observed for a total response rate of 38%. The median time to progression was 138 days. Grade 3-4 toxicity included fatigue (n=3), neutropenia (n=2), thrombocytopenia (n=2), interstitial pneumonitis (n=1), stomatitis (n=1) and diarrhea (n=1). Clinical activity was associated with a higher area under the curve (AUC) and maximal reduction in phosphorylated p70(S6)K and 4EBP1 in peripheral blood mononuclear cells. At the dose and schedule used, temsirolimus had low single agent activity. Investigation of alternate dosing schedules and use in combinations is indicated.