Altus Pharmaceuticals Reports Last Patient Visit Of Trizytek(TM) Phase 3 Efficacy Trial.

Trizytek Clinical Program Demonstrates Commitment to Advancing Enzyme Replacement Therapy Options for Cystic Fibrosis Patients

CAMBRIDGE, Mass. -- Altus Pharmaceuticals Inc. (NASDAQ: ALTU), a biopharmaceutical company focused on oral and injectable protein therapeutics for gastrointestinal and metabolic disorders, announced today the completion of the last patient visit of the Trizytek Phase 3 efficacy trial. In this trial, Altus is evaluating the efficacy of an oral, non-porcine enzyme replacement therapy for cystic fibrosis patients with exocrine pancreatic insufficiency. Derived from recombinant technology, Trizytek [porcine-free enzymes] is a consistent, 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.

"Completing the last patient visit of the Phase 3 efficacy trial marks an important milestone in the development of Trizytek. This news confirms that we are on track to report top-line Trizytek efficacy data in the third quarter of 2008," stated Dr. Georges Gemayel, President and Chief Executive Officer of Altus Pharmaceuticals. "We are pleased to report that 134 patients completed the efficacy trial, of which approximately 30 percent were in the severe malabsorption group, with baseline CFAs below 40 percent. We believe that both the total number of patients completing the trial and the number in the severe malabsorption group are consistent with the special protocol assessment that was discussed and agreed upon between Altus and the FDA."

The DIGEST trials - - Determining the efficacy and safety of an Innovative GastrointESTinal enzyme complex - - are Altus Pharmaceuticals' Phase 3 clinical program. The DIGEST efficacy trial tested a one capsule per-meal dosing regimen and will study fat, protein and carbohydrate absorption in cystic fibrosis patients with exocrine pancreatic insufficiency. In parallel with the efficacy trial, Altus is conducting a long-term safety study to evaluate Trizytek following one year of open-label treatment.

Dr. Gemayel continued, "Our Phase 3 Trizytek clinical program is the largest and most scientifically robust ever conducted to evaluate the efficacy and safety of enzyme replacement therapy and it demonstrates our commitment to advancing enzyme replacement therapy options for both cystic fibrosis patients and others who suffer from pancreatic insufficiency."

Dr. Gemayel concluded, "Because of the uncertainties that exist with therapeutics that contain animal-derived ingredients, we believe there is a need, now more than ever, for new products that are derived from recombinant technology such as Trizytek."

About Trizytek [porcine-free enzymes]

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.

About The Current Pancreatic Enzyme Replacement Market

The existing animal-derived pancreatic enzyme replacement products have been marketed since before the enactment of the Food, Drug and Cosmetic Act in 1938 and are not marketed under new drug applications, or NDAs, approved by the United States Food and Drug Administration, or FDA. In April 2004, the FDA issued a notice that manufacturers of existing pancreatic enzyme replacement products will be subject to regulatory action if they do not obtain approved NDAs for those products by April 28, 2008. In October 2007, the FDA issued an update to the 2004 notice and announced that it has extended the deadline for unapproved pancreatic enzyme drug products from April 28, 2008 to April 28, 2010, but only if the manufacturers have investigational new drug applications on active status on or before April 28, 2008 and have submitted NDAs on or before April 28, 2009. According to IMS Health, global prescription sales of existing pancreatic enzyme replacement products were approximately $858 million in 2007.

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. Trizytek[TM] is a trademark of Altus Pharmaceuticals.

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 our Trizytek clinical trials, including the expected time for reporting and filing of results, and the ultimate outcome or results in our Trizytek clinical trials and development program. Any or all of the forward-looking statements in this press release may turn out to be wrong. 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.