Altus Pharmaceuticals Announces Positive Results from Phase II Study in Growth Hormone Deficient Patients with Once-Per-Week Growth Hormone.

CAMBRIDGE, Mass. -- Altus Pharmaceuticals Inc. (Nasdaq: ALTU), a biopharmaceutical company focused on the development and commercialization of oral and injectable protein therapeutics for patients with gastrointestinal and metabolic diseases, today announced results from a multi-center Phase II clinical trial in growth hormone deficient adults for ALTU-238, a long-acting crystalline formulation of recombinant human growth hormone (hGH, somatropin). ALTU-238 is being developed as a subcutaneously administered, once-per-week formulation of human growth hormone that employs Altus' proprietary protein crystallization and formulation technology.

The Phase II clinical trial was conducted using two dose levels of ALTU-238 in adults with growth hormone deficiency. The primary objectives of the trial were to determine the safety and tolerability of ALTU-238, as well as to evaluate its pharmacokinetic and pharmacodynamic profile. ALTU-238 was administered once-per-week, using a fine 30-gauge needle, over a three-week period. The results of this trial confirmed results of earlier Phase I studies of ALTU-238 in which the pharmacokinetic and pharmacodynamic profile observed was supportive of a once-per-week injection of ALTU-238. The study identified doses of ALTU-238 that maintained IGF-1 levels within the normal range for age and gender over the course of the study. Once-per-week dosing of ALTU-238 appeared to result in a consistent, linear dose response of hGH and IGF-1 levels in the blood. Altus anticipates that these positive results will support dose selection for ALTU-238 in upcoming Phase III trials in adults and pediatric patients which we anticipate will start later this year.

ALTU-238 was shown to be well-tolerated by patients enrolled in the study with generally mild injection site reactions being the most commonly reported event. No serious adverse events or antibody formations were reported. The Company expects to present the full results of the study at an upcoming medical meeting later in the year.

Sheldon Berkle, President and Chief Executive Officer of Altus Pharmaceuticals said, "We are greatly encouraged by these study results and the potential to provide patients with a safe, effective long-acting treatment option, with fewer injections than current products which require daily injections. ALTU-238 could represent a significant milestone in the treatment of growth hormone disorders, offering greater patient convenience, comfort and improved compliance. We are looking to gain agreement with the regulatory authorities on the upcoming Phase III programs for both adult and pediatric patients with a goal of quickly bringing this product to patients."

"We believe that these positive Phase II data indicate that our proprietary protein crystallization technology can effectively deliver long-acting growth hormone therapy to growth hormone deficient patients through a once-weekly injection using a fine-gauge needle," said Dr. Alexey Margolin, Chief Scientific Officer at Altus Pharmaceuticals. "In a number of clinical trials - including a large multi-center Phase II study with our orally administered enzyme replacement therapy for pancreatic insufficiency and now our Phase I and II growth hormone studies - our proprietary crystallization and formulation technology has repeatedly demonstrated the potential to be a robust platform for development of both oral and injectable biopharmaceuticals."

About ALTU-238

ALTU-238 is a long-acting subcutaneous formulation of recombinant human growth hormone that employs Altus' proprietary protein crystallization and formulation technology. Altus' technology preserves the structure of the human growth hormone molecule without the need for polymers or encapsulation and enables ease of administration through a fine gauge needle. Recombinant human growth hormone is approved for treating multiple growth disorders in children, adolescents and adults. Global sales of recombinant human growth hormone were approximately $2.4 billion in 2005.

About Growth Hormone Deficiency and Growth Failure

Growth hormone disorders occur when the production of growth hormone, secreted via the hypothalamic-pituitary axis (GHRH-GH-IGF1), is disrupted. Growth hormone plays a critical role in stimulating bone growth and development and it is involved in the production of muscle and in the breakdown of fats. In children, when there is a complete absence of growth hormone, severe growth retardation results. When there is a partial deficiency of growth hormone in children, short stature results. Recombinant human growth hormone (rhGH) products are currently approved to treat multiple growth disorders, including pediatric and adult growth hormone deficiency, Turner Syndrome, chronic renal insufficiency, idiopathic short stature, Prader-Willi Syndrome, short children born small for gestational age, short bowel syndrome and muscle wasting in patients with HIV.

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's website is http://www.altus.com.

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, the anticipated timing for enrollment in the Phase III clinical trial of ALTU-238, and the ability of Altus' proprietary protein crystallization technology to effectively deliver growth hormone therapy through a once-weekly injection using a fine gauge needle. 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 success of ongoing and planned 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 Annual Report on Form 10-K for the fiscal year ended December 31, 2005. However, Altus undertakes no obligation to publicly update forward-looking statements, whether because of new information, future events or otherwise.