BioMarin Pharmaceutical ( BMRN) said Monday that it would try to raise additional funds through a stock offering and a convertible debt offering worth about 25% of its current market capitalization.

The Novato, Calif., drug company said it will offer 9 million common shares and $125 million of senior subordinated convertible notes in separate issues. BioMarin said it would use the proceeds to market existing drugs and to finance clinical trials for experimental medications, as well as for general corporate purposes.

BioMarin might use some of the proceeds to purchase all or some of its 3.5% convertible subordinated notes due in 2008.

The announcement sent BioMarin's shares down 47 cents, or 3.3%, to $13.96 on heavier-than-average trading. The stock slipped as low as $13.69.

BioMarin hasn't set a price for its stock offering, but it predicted net proceeds would be $123.1 million on the basis of Friday's closing price of $14.43. The company could get up to $141.6 million if high demand for the stock prompts underwriters to exercise their right to buy an additional 1.35 million shares. BioMarin now has 74.75 million shares outstanding and a market capitalization of just above $1 billion.

The debt offering has a provision to offer another $18.75 million in senior subordinated convertible notes due in 2013 if there is high demand. BioMarin expects net proceeds of $121 million to $139.2 million from the debt sale.

BioMarin's money-raising efforts follow by several days favorable news of a late-stage clinical trial for Phenoptin, a treatment for phenylketonuria, or PKU. BioMarin says some 50,000 diagnosed patients in the developed world have PKU, an enzyme-deficiency disorder that can cause mental retardation and brain damage, mental illness, seizures and tremors.

The company's partner in developing and marketing the drug is the Swiss biotech company Serono ( SRA).