Phase I Study of DOXIL and Temsirolimus in Resistant Solid Malignancies

Rationale: The Mammalian Target of Rapamycin (mTOR) is a large polypeptide serine/threonine kinase of 289 kDa; kinases have been shown to be important regulators of cancer cell cycle, proliferation, invasion, and angiogenesis, and mTOR has been shown to have a key role in the signaling of malignant cell growth, proliferation, differentiation, migration, and survival. Inhibition of mTOR would result in arrest of cell growth in the G1 phase of the cell cycle. Temsirolimus (CCI-779) is a soluble ester analogue of rapamycin (sirolimus) which has shown impressive in vitro and in vivo cytostatic activity in selectively inhibiting mTOR. In animal models, temsirolimus has demonstrated an impressive cytostatic effect on a wide variety of cancer cells. In vitro, it inhibited the growth of human T-cell leukemia, glioblastoma, melanoma, prostate, breast, renal cell, and pancreatic cells, all of which showed particular sensitivity to temsirolimus, with significant growth inhibition at concentrations of less that 0.01micrometer. In Phase I trials, temsirolimus has been investigated as a single agent on a weekly schedule as well as daily for 5 days every other week, and evidence of activity was observed over the entire dose range (15 - 220 mg/m2) in patients with both breast and renal cancer. There was no apparent relationship between exposure and clinical benefit, suggesting that the inhibition of mTOR may be achieved at doses well below dose levels that result in dose limiting toxicities. Major tumor responses were noted in Phase I trials in patients previously treated with lung, breast, renal as well as neuroendocrine tumors. Minor responses were noted in soft tissue sarcoma, endometrial, and cervical carcinoma. Pegylated liposomal doxorubicin has been FDA approved for use in refractory metastatic ovarian cancer and AIDS-related Kaposi's Sarcoma. It has also been shown to be effective in previously treated metastatic breast cancer. Combination studies in preclinical models