ARISTA PLACE

Exhibit 10.4

ARISTA PLACE

000 Xxxxxxxx Xxxx., Xxxxx 000

Broomfield, CO 80021

p. 303.460.8800

f. 303.280.5155

May 16, 2013

Mr. Xxx Xxxxxxx

ARCA Biopharma

0000 Xxxxxx Xxxxx

Broomfield, CO 80021

Dear Xxx:

RE: THREE-MONTH EXTENSION

Arista Place, LLC (Landlord) agrees to a continuation of the Term of your lease for an additional three (3) month period.  The financial terms presently applied to the ARCA (Tenant) lease obligations will remain the same during this additional three (3) month term.

The end of your Term will now be September 30, 2013.  Your Rate and CAM charges will continue as is and the Landlord will continue to bill this monthly.

If the above is satisfactory to you and ARCA, please sign, date, and witness below.

Sincerely,

/s/ Xxxxxxx X. Xxxxx

Xxxxxxx X. Xxxxx

Manager

		AGREED & ACCEPTED:
		ARCA Biopharma
/s/ Xxxxxxx Xxxxxxx		/s/ Xxx Xxxxxxx
Witness		Xxx Xxxxxxx, CFO