Phase 1b Neoadjuvant Run-In Study With TAK-228 Followed by Letrozole/TAK-228 in Women With High-Risk ER+/HER2- Breast Cancer

Millennium has developed TAK-228, which is a novel, highly selective, orally bioavailable adenosine 5' triphosphate (ATP)-competitive inhibitor of the serine/threonine kinase referred to as the mechanistic target of rapamycin (mTOR). TAK-228 (formerly INK128 or MLN0128) targets 2 distinct multiprotein complexes, mTORC1 and mTORC2. TAK-228 selectively and potently inhibits mTOR kinase (IC50 = 1.1 nM), inhibits mTORC1/2 signaling, and prevents cellular proliferation.

The mTOR complex (mTORC) is an important therapeutic target that is generally stable (i.e., low tendency to mutate) and is a key intracellular point of convergence for a number of cellular signaling pathways. Inhibiting mTOR may inhibit abnormal cell proliferation, tumor angiogenesis, and abnormal cellular metabolism, thus providing the rationale for mTOR inhibitors as potential agents in the treatment of a number of indications including solid tumor and hematological malignancies, as either monotherapy or in combination with other chemotherapeutic agents. Like rapamycin, several newly approved rapalogs (temsirolimus and everolimus) are specific and allosteric inhibitors of mTORC1, and only partially inhibit mTORC1 signaling pathways. They do not directly inhibit mTORC2, which has shown to be an emerging target in cancer research. TAK-228 was developed to address the incomplete inhibition of the mTOR pathway by rapalogs.

Eligible subjects will have a research biopsy and baseline blood and urine studies done within two weeks prior to start of study treatment. Subjects will then be treated with TAK-228 for 10 days, and a repeat biopsy and pharmacokinetics will be done on day 11.

The subject will then be treated with the combination of TAK-228 and letrozole for an additional 110 days, before undergoing resection of the primary tumor. Subjects will be treated at the recommended Phase II dose of TAK-228 of 3 mg once daily, and a dose deescalation to 2 mg daily will be performed if dose-limiting toxicity is seen in 1/3 or more of the subjects at the first dose level. The maximum tolerated dose cohort will be expanded to include six to ten subjects.