Altus Pharmaceuticals Reports Positive ALTU-237 Pre-Clinical Data for Reducing Hyperoxaluria, a Precusor to Kidney Stone Formation.

Company's Product Pipeline Continues to Evolve

Altus Plans to File ALTU-237 Investigational New Drug Application in the First Half of 2007

CAMBRIDGE, Mass. -- Altus Pharmaceuticals Inc. (NASDAQ: ALTU), a biopharmaceutical company focused on oral and injectable protein therapeutics for patients with gastrointestinal and metabolic disorders, today announced the presentation of positive pre-clinical data for ALTU-237 at the American Society of Nephrology's (ASN) Renal Week annual meeting. The ALTU-237 presentation title was "Crystalline Formulation of an Orally Administered Oxalate Degrading Enzyme Reduces Hyperoxaluria in a Mouse Genetic Model." The pre-clinical results showed that four weeks of therapy with ALTU-237 resulted in a sustained reduction of urinary oxalate in an animal model with primary hyperoxaluria. The ALTU-237 data was presented at one of ASN's symposia session titled "Renal Stones: Another Hard Topic," which was held on Sunday, November 19, 2006.

About ALTU-237

ALTU-237, Altus Pharmaceuticals' lead pre-clinical product candidate, is an orally-delivered crystalline formulation of an oxalate-degrading enzyme that Altus designed for the treatment of primary hyperoxaluria and enteric hyperoxaluria, as well as the prevention of recurrent kidney stones in individuals with a high risk or history of kidney stones.

Altus Pharmaceuticals expects to file an investigational new drug (IND) application for ALTU-237 in the first half of 2007. The ALTU-237 program, if approved, will be Altus Pharmaceuticals' third clinical program that is based on the Company's proprietary protein crystallization technology. Altus' first two clinical programs, ALTU-135 and ALTU-238, have completed Phase II clinical trials. On November 15, 2006, Altus Pharmaceuticals announced that it plans to initiate its Phase III clinical trial for ALTU-135 in Cystic Fibrosis patients with pancreatic insufficiency in the second quarter of 2007.

About Hyperoxaluria

Hyperoxaluria is a disease characterized by excessively high levels of oxalate in the urine, which can be a precursor to forming kidney stones. Hyperoxaluria can be caused by either excessive absorption of dietary oxalate (enteric hyperoxaluria) or increased endogenous production of oxalate (primary hyperoxaluria). When untreated, primary hyperoxaluria could lead to recurrent kidney stones and could contribute to renal failure. Ultimately, patients suffering from severe primary hyperoxaluria experience calcium deposits in their organs, which, left untreated, could lead to death.

"This pre-clinical data is very encouraging and we look forward to starting our clinical program with ALTU-237 next year," commented Alexey Margolin, Senior Vice President of Research and Pre-Clinical Development and Chief Scientific Officer at Altus Pharmaceuticals. "Hyperoxaluria presents a significant unmet clinical need. There are no current effective pharmacological treatments for primary hyperoxaluria, enteric hyperoxaluria or recurrent kidney stones. We believe ALTU-237 could be the first effective therapeutic agent specifically designed to reduce oxalate levels and prevent the formation of kidney stones."

Study Methods:

* For this ALTU-237 pre-clinical study, hyperoxaluria reduction was measured in a genetic mouse model for primary hyperoxaluria. To mimic the human disease, which involves nephrocalcinosis, renal failure and potentially death, the mice were further challenged with ethylene glycol.

Key Results:

* Four weeks of oral therapy with ALTU-237 resulted in a sustained reduction of urinary oxalate levels.

* A reduction in urinary oxalate of 30 to 50 percent in all treatment groups, compared to controls, was achieved.

* A reduction in nephrocalcinosis and an increase in survival rate was observed in the two lower dose groups.

* There was no nephrocalcinosis, renal failure or death in the high dose group.

Study Conclusion: We believe that these pre-clinical results demonstrate that ALTU-237 could have the potential to be a new oral therapeutic agent for the treatment of primary hyperoxaluria.

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 has headquarters in Cambridge, Massachusetts, and is listed on the NASDAQ Global Market under the symbol ALTU. For additional information about the company, please visit www.altus.com.

Safe Harbor Statement

Certain statements in this news release concerning Altus Pharmaceuticals' 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 filing of an Investigational New Drug application for ALTU-237 in the first half of 2007, plans for initiating a Phase III trial of ALTU-135 in the second quarter of 2007, the Company's encouragement from the pre-clinical results of ALTU-237 and the potential start of its clinical program next year, and the potential for ALTU-237 to be the first effective therapeutic agent specifically designed to reduce oxalate levels, prevent the formation of kidney stones and treat primary hyperoxaluria. 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 Pharmaceuticals might make or by known or unknown risks and uncertainties, including, but not limited to uncertainties as to the future success of ongoing and planned clinical trials; regulatory approvals; the possibility that results demonstrated in earlier pre-clinical and clinical trials may not be achieved in later-stage 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 Pharmaceuticals ' reports filed with the Securities and Exchange Commission, including its Annual Report on Form 10-K for the fiscal year ended December 31, 2005, as may be updated in its quarterly and current reports. However, Altus Pharmaceuticals undertakes no obligation to publicly update forward-looking statements, whether because of new information, future events or otherwise.