Cubist Pharmaceuticals (CBST) 8-K/A Financial Statements and Exhibits

EXHIBIT 23.1

Consent of Independent Registered Public Accounting Firm

We consent to the incorporation by reference in this Current Report on Form 8-K/A and the Registration Statements on Form S-3 (No. 333-170001) and Form S-8 (Nos. 333-168459, 333-162764, 333-162763, 333-155352, 333-148455, 333-148454, 333-136937, 333-132248, 333-126225, 333-124210, 333-118065, 333-106388, 333-101908, 333-99739, 333-60168, 333-60152, 333-54140, 333-49522, 333-32178, 333-65385, 333-65383, and 333-25707) of Cubist Pharmaceuticals, Inc. of our report dated March 18, 2013, with respect to the financial statements of Optimer Pharmaceuticals, Inc., included in Optimer Pharmaceuticals, Inc.’s Annual Report (Form 10-K) for the year ended December 31, 2012 filed with the Securities and Exchange Commission.

	/s/ Ernst & Young, LLP
San Diego, California
December 17, 2013