April 4, 2014

Securities and Exchange Commission

100 F Street, N.E.

Washington, DC  20549

Commissioners:

We have read the statements made by Retrpohin, Inc. under Item 4.01 of its Form 8-K dated March 31, 2014. We agree with the statements concerning our Firm in such Form 8-K; we are not in a position to agree or disagree with other statements of Retrpohin, Inc. contained therein.

Very truly yours,

/s/ Marcum llp

Marcum llp