Exhibit 10.28

CDC IV, LLC

47 HULFISH STREET, SUITE 310

PRINCETON, NEW JERSEY 08542

September 5, 2007

BioDelivery Sciences International, Inc.

Arius Pharmaceuticals, Inc. and

Arius Two, Inc.

2501 Aerial Center Parkway, Suite 205

Morrisville, North Caroline 27560

Attn: Mark A. Sirgo, President and Chief Executive Officer

RE: Clinical Development and License Agreement

Dear Mr. Sirgo:

The purpose of this letter (this “Letter Agreement”) is to set out certain understandings and agreements between (i) CDC IV, LLC (“CDC”) and (ii) BioDelivery Sciences International, Inc. (“BioDelivery”), Arius Pharmaceuticals, Inc., a wholly-owned subsidiary of BDSI (“Arius”) and Arius Two, Inc., a wholly-owned subsidiary of BioDelivery (“Arius Two”).

Reference is hereby made to that certain Clinical Development and License Agreement (as amended, the “CDC License”), dated as of July 14, 2005 among CDC (as successor in interest to Clinical Development Capital LLC), BioDelivery and Arius. Pursuant to the terms of the CDC License, BioDelivery, Arius and Arius Two have requested that CDC consent to, among other things, (i) the acquisition by Arius Two of certain assets related to the BEMA Fentanyl product from QLT USA, Inc., and (ii) the amendment of the CDC License in connection with such acquisition and the subsequent license of certain rights with respect to such assets by Arius to Meda AB; in each case pursuant to the terms of (A) that certain Sublicensing Consent and Amendment, entered into as of the date hereof, by BDSI, Arius and CDC (the “Sublicensing Consent”) and (B) that certain BEMA Acquisition Consent, Amendment and Waiver, entered into as of the date hereof, by BDSI, Arius, Arius Two and CDC (the “Acquisition Consent” and together with the Sublicensing Consent, collectively, the “CDC Consents”). As a condition to CDC entering into the CDC Consents, CDC is requiring BDSI, Arius and Arius Two to enter into this Letter Agreement. Capitalized terms used herein, but not otherwise defined herein, shall have the meanings set forth in the Acquisition Consent.

1. Defaults and Terminations under the New License . Notwithstanding anything to the contrary set forth in the CDC License, the QLT License, the New License, the Acquisition Agreements, the CDC Consents or any agreements entered into by any of BDSI, Arius or Arius Two in connection with any of the foregoing, BDSI, Arius and Arius Two hereby agree and acknowledge that (i) in no event shall Arius Two declare any default against Arius under the New License, or otherwise