October 23, 2008

Altus Pharmaceuticals Announces Presentation of Phase 3 Trizytek Efficacy Data at the North American Cystic Fibrosis Conference

Altus Pharmaceuticals Inc. (NASDAQ: ALTU) announced today that the Trizytek( TM) (liprotamase) Phase 3 efficacy study results will be presented at oral and poster sessions at the 2008 North American Cystic Fibrosis Conference (NACFC) in Orlando, FL on October 23 and 24. Trizytek is a non-porcine derived enzyme replacement therapy for patients with pancreatic insufficiency. The Phase 3 Trizytek efficacy results will be presented by Dr. Drucy Borowitz, Professor of Clinical Pediatrics, State University of New York, Director, Cystic Fibrosis Center, Women and Children's Hospital of Buffalo and principal investigator for the Trizytek Phase 3 trials.

Altus' Phase 3 Trizytek efficacy trial in patients with cystic fibrosis (CF) successfully met its primary endpoint of improvement in fat absorption with statistical significance. In August 2008, the Company released top-line results from its 163 patient, double-blind, placebo-controlled trial of Trizytek, which is a stable and pure combination of three active enzymes in a fixed-ratio that is designed to improve fat, protein and carbohydrate absorption in pancreatic insufficient individuals. (Click here to view the August 11, 2008 press release.) Trizytek was well-tolerated and had a favorable safety profile in the trial. There were no serious adverse events attributed to the Trizytek treatment. Altus' Trizytek Phase 3 clinical program is the largest ever conducted to evaluate the efficacy and safety of pancreatic enzyme replacement therapy in cystic fibrosis patients.

Commenting on Trizytek, Dr. Drucy Borowitz said, "I believe the Trizytek data are very encouraging for cystic fibrosis patients who need pancreatic enzyme replacement therapy. Despite the current availability of porcine-derived enzyme products, I believe there is a significant need for new FDA-approved options that may offer enhanced safety and improve the overall quality of life for patients. Trizytek is the pancreatic enzyme replacement therapy that has been the most thoroughly studied, with clinical results from more than 300 patients. I believe this innovative product has the potential to enhance nutritional status for CF patients and provide a pure alternative to porcine-derived enzymes."

"We are dedicated to driving Trizytek to commercialization," stated Dr. Georges Gemayel, President and Chief Executive Officer of Altus Pharmaceuticals. "After extensive review of the entire Phase 3 efficacy data package as well as the ongoing long-term safety and outcomes studies, we strongly believe that Trizytek can benefit patients and we look forward to working with the FDA to make this drug commercially available. We are focusing our Trizytek resources on moving all aspects of the program forward and our objective is to file a new drug application with the FDA in the first half of 2009."

The Company has a pre-NDA meeting scheduled for mid-November to discuss the Trizytek data package with the FDA.

Dr. Gemayel continued, "For pancreatic insufficient patients, the most relevant measure of success is long-term health outcomes, such as weight and height maintenance or gain. We are looking at these as well as other overall health outcomes in the Trizytek long-term studies that are evaluating patients exposed to Trizytek for one year. Preliminary data from the open-label long-term studies suggest that adults are maintaining their weight and BMI percentiles and children are maintaining their height and weight percentiles with continued Trizytek treatment. We believe the information from more than the 200 patients from these studies will be extremely powerful in differentiating Trizytek from all other enzyme replacement products. We are on track to complete these studies, as expected, in the first half of 2009."

In conjunction with this news release, Altus has produced an audio news release for Trizytek. (Click here to listen to the audio news release.)

About Trizytek(TM) (liprotamase)

Trizytek has the potential to be the first porcine-free enzyme replacement therapy for patients with pancreatic insufficiency. Pancreatic insufficiency is a condition that affects most cystic fibrosis patients, as well as many patients with chronic pancreatitis. In these diseases, a deficiency of pancreatic enzymes causes poor absorption of essential nutrients, which often leads to malnutrition, impaired growth and reduced survival. Trizytek is intended to replace missing digestive enzymes with one capsule per-meal to promote and maintain proper digestion and growth in affected patients. Altus is developing Trizytek to enhance health outcomes by offering significant patient advantages such as improved and more consistent dosing that we expect will drive better long-term compliance. Utilizing recombinant technology, Trizytek is manufactured by blending three drug substance enzymes: lipase, protease and amylase. This consistent and pure enzyme combination is designed to improve fat, protein and carbohydrate absorption in pancreatic insufficient individuals.

About Altus Pharmaceuticals Inc.

Altus Pharmaceuticals, headquartered in Cambridge, MA, 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 is listed on the Nasdaq Global Market under the symbol ALTU.

Safe Harbor Statement

The statements in this press release regarding the assessment of the Phase 3 data and its implications for remaining Phase 3 trials, the future development of Trizytek, and our ability to file an NDA and the timing of any filing of an NDA with the FDA for Trizytek are forward-looking statements that are subject to risks and uncertainties that could cause actual results to differ materially from those expressed or implied by such statements. In particular, these statements are subject to the risk that further analyses of the Phase 3 data may lead to different interpretations of the data than the analyses conducted to date and/or may identify important implications of the Phase 3 data that are not reflected in these statements. In addition, further analyses of the Phase 3 data and discussion with regulatory authorities may lead to important modifications to the development plan for Trizytek, including delays in commercialization. Our ability to file an NDA with the FDA for Trizytek will also depend on our ability to commit sufficient financial resources to the project, which resources may be unavailable to us or may be deployed for other purposes. There can be no assurance that Trizytek will ever receive regulatory approval or be successfully commercialized. Other risks and uncertainties that could cause actual results to differ materially from those expressed or implied by these forward-looking statements include those detailed from time to time in the Company's periodic reports filed with the Securities and Exchange Commission, including the Company's current reports on Form 8-K, quarterly reports on Form 10-Q and annual report on Form 10-K, particularly the discussion under the caption "Item 1A, Risk Factors" in the Company's Quarterly Report on Form 10-Q for the quarter ended June 30, 2008, which was filed with the Securities and Exchange Commission on August 5, 2008. The forward-looking statements in this press release are qualified by these risk factors. We assume no obligation to publicly update any forward-looking statements, whether as a result of new information, future developments or otherwise.

Altus and the Altus logo are the registered trademarks of Altus Pharmaceuticals. Trizytek and DIGEST Trials are trademarks of Altus Pharmaceuticals.