AGREEMENT REGARDING JOINT FILING OF STATEMENT ON SCHEDULE 13D OR 13G

CUSIP No. 00000X000

EXHIBIT A

AGREEMENT REGARDING JOINT FILING

OF STATEMENT ON SCHEDULE 13D OR 13G

The undersigned agree to file jointly with the Securities and Exchange Commission (the “SEC”) any and all statements on Schedule 13D or Schedule 13G (and any amendments or supplements thereto) required under section 13(d) of the Securities Exchange Act of 1934, as amended, in connection with purchases and sales by the undersigned of the securities of any issuer until such time as the undersigned file with the SEC a statement terminating this Agreement Regarding Joint Filing of Statement on Schedule 13D or 13G.  For that purpose, the undersigned hereby constitute and appoint Palo Alto Investors, LLC, a California limited liability company, as their true and lawful agent and attorney-in-fact, with full power and authority for and on behalf of the undersigned to prepare or cause to be prepared, sign, file with the SEC and furnish to any other person all certificates, instruments, agreements and documents necessary to comply with section 13(d) and section 16(a) of the Securities Exchange Act of 1934, as amended, in connection with said purchases and sales, and to do and perform every act necessary and proper to be done incident to the exercise of the foregoing power, as fully as the undersigned might or could do if personally present, until such time as the undersigned file with the SEC a statement terminating this Agreement Regarding Joint Filing of Statement on Schedule 13D or 13G.

Dated:              November 12, 2013

PALO ALTO HEALTHCARE MASTER FUND II, L.P.				PALO ALTO INVESTORS, LLC
By:	Palo Alto Investors, LLC, General Partner			By:	/s/ Xxxxx Xxxxx
					Xxxxx Xxxxx, Chief Operating Officer
By:	/s/ Xxxxx Xxxxx
	Xxxxx Xxxxx, Chief Operating Officer

	/s/ Xxxxxxx Xxx				/s/ Xxxxxxx Xxxxxxxx Xxx
	Xxxxxxx Xxx, MD				Anthony Joonkyoo Yun, MD