Altus Pharmaceuticals Reports First Quarter Results.

- - Trizytek(TM) Efficacy Trial Enrollment Complete - -

- - 175 Patients Enrolled in Trizytek Safety Study - -

CAMBRIDGE, Mass. -- Altus Pharmaceuticals Inc. (NASDAQ: ALTU), a biopharmaceutical company focused on oral and injectable protein therapeutics for gastrointestinal and metabolic disorders, today reported financial results for the quarter ended March 31, 2008.

First Quarter 2008 Results

For the first quarter of 2008, the Company reported a net loss attributable to common stockholders of $24.6 million, or $0.80 per share, compared to a net loss attributable to common stockholders of $15.8 million, or $0.67 per share, in the first quarter of 2007. Revenues were $2.6 million in the first quarter of 2008 compared to $827,000 the first quarter of 2007. The increase in first quarter revenue is primarily attributable to revenue associated with the Company's agreement with Cystic Fibrosis Foundation Therapeutics, Inc. for the development of Trizytek(TM) [porcine-free enzymes] (formerly ALTU-135) as well as additional revenue from Genentech, Inc. in the first quarter of 2008. Cash, cash equivalents and marketable securities at March 31, 2008 were $118.0 million.

Research and development expenses totaled $21.6 million in the first quarter of 2008 compared to $12.9 million in the first quarter of 2007. The increase in R&D expenses is primarily due to an increase in development costs relating to conducting the Trizytek Phase 3 safety and efficacy trials.

General and administrative expenses were $5.8 million in the first quarter of 2008 compared to $4.6 million in the first quarter of 2007. The increase in G&A expenses was primarily driven by a one-time charge of $600,000 associated with a separation agreement with Altus' former chief executive officer as well as increased recruiting costs related to the search for a new CEO.

"Altus is advancing a robust product pipeline of crystallized protein therapies. We are committed to bring these new therapies to patients with our initial focus on driving Trizytek to commercialization," stated Dr. David Pendergast, Executive Chairman of Altus Pharmaceuticals. "We are pleased to report that the patient enrollment phase of the Trizytek efficacy trial is complete and we continue to be confident that we will report top-line efficacy results in the third quarter. The safety study has 175 patients currently enrolled, which is sufficient for the one-year safety data on the required 100 patients to be included in our NDA filing in the first half of 2009."

Dr. Pendergast continued, "We look forward to initiating and completing this summer the ALTU-238 Phase 1c study, which we expect will include 36 patients. This trial is designed to confirm that the ALTU-238 material, produced at the current increased manufacturing scale, performs similar to the material used in previous studies."

Dr. Pendergast concluded, "The Altus team is very focused on continuing to move our clinical programs forward. We are well positioned for success with a pipeline consisting of three products in human clinical development and two products that are in preclinical testing. We believe the next several months will be a very exciting time as we plan to achieve several key milestones: releasing ALTU-237 Phase 1 data in the second quarter; reinitiating the ALTU-238 development program in the third quarter; and reporting top-line Trizytek Phase 3 efficacy results in the third quarter."

Conference Call Access Information

The Company will host a conference call to discuss the results at 11:00 a.m. ET on May 7. The call may be joined via telephone by dialing [phone] or 719-325-4881 (for international participants) at least 5 minutes prior to the start of the call. The conference confirmation code is: 7245147. For 72 hours following the call, an audio replay can be accessed by dialing [phone] or [phone] and using the conference confirmation code 7245147.

A live audio webcast of the call will also be available on the "Investor Relations" section of the Company's website, www.altus.com. An archived audio webcast will be available on the Altus website approximately two hours after the event and will be archived for 30 days.

About Altus Pharmaceuticals Inc.

Altus Pharmaceuticals is a biopharmaceutical company focused on the development and commercialization of oral and injectable protein therapeutics for patients with gastrointestinal and metabolic disorders. The Company's website is http://www.altus.com.

Safe Harbor Statement

Certain statements in this news release concerning Altus' business are considered "forward-looking statements" within the meaning of the Private Securities Litigation Reform Act of 1995. These statements include, but are not limited to, those relating to the expected enrollment and completion of our Trizytek, ALTU-238 and ALTU-237 clinical trials, the expected time for completion, reporting and filing of results in our Trizytek and ALTU-237 clinical trials, the timing for planned initiation of clinical trials for ALTU-238, the expectation that the Company achieves its other goals and milestones, including, without limitation, obtaining resources to advance ALTU-237 into a Phase 2 trial, and to initiate a Phase 2 ALTU-238 pediatric trial. Any or all of the forward-looking statements in this press release may turn out to be wrong. They can be affected by inaccurate assumptions Altus might make or by known or unknown risks and uncertainties, including, but not limited to uncertainties as to the future cost, timing, enrollment and success of ongoing and planned clinical trials; the risk of demonstrating the ultimate potential of our product pipeline; the continuing risks associated with the development and manufacture of products to supply the clinical trials and the unproven safety and efficacy of products under development. Consequently, no forward-looking statement can be guaranteed, and actual results may vary materially. Additional information concerning factors that could cause actual results to materially differ from those in the forward-looking statements is contained in Altus' reports to the Securities and Exchange Commission, including its Quarterly Report on Form 10-Q for the quarter ended March 31, 2008. However, Altus undertakes no obligation to publicly update forward-looking statements, whether because of new information, future events or otherwise.

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