Rigel Pharmaceuticals Inc.'s $48.8 million public offering follows a busy 18 months.

Back in December 2005, the South San Francisco-based company's stock plummeted when a Phase II trial of SYK kinase inhibitor R112 for allergic rhinitis missed its endpoints. But since then, Rigel has moved another SYK kinase inhibitor into two Phase II trials and a Phase I/II trial, all while continuing its early stage discovery work and advancing new programs toward the clinic. (See BioWorld Today, Dec. 2, 2005.)

All of that activity translates into a burn rate of about $50 million, according to Raul Rodriguez, executive vice president and chief operating officer for Rigel. With $104.5 million in cash and available securities as of Dec. 31, Rodriguez projected the company will end 2007 with about two years worth of cash on hand, thanks to the financing.

The sale of 5 million shares at $9.75 per share will net Rigel $45.5 million after fees and expenses, or $52.4 million if the underwriters exercise their option to an additional 750,000 shares to cover overallotments. Credit Suisse Securities LLC and Lehman Brothers Inc. are acting as joint bookrunners, with Thomas Weisel Partners LLC serving as co-manager for the offering, which is expected to close May 8.

The $9.75 sale price represents a discount to Rigel's Wednesday closing price of $10.19. Shares (NASDAQ:RIGL) traded down 55 cents on Thursday to close at $9.64.

Proceeds from the offering will support ongoing and planned clinical trials with SYK kinase inhibitor R788. Rigel started a Phase II ascending-dose trial of the drug in rheumatoid arthritis last fall, and so far it appears to be well tolerated, although top-line data aren't expected until the second half of this year. Rigel also recently began an exploratory Phase II trial of R788 in immune thrombocytopenia purpura, and the initial data demonstrating raising platelet counts prompted the company to expand the trial. Top-line data now are expected by the end of the year.

Just last month, Rigel initiated a third program with R788, this time a Phase I/II trial in B cell lymphoma. The company expects interim results in the second half of this year and top-line data next year.

Beyond R788, Rigel remains committed to its goal of filing one new investigational new drug application each year - a goal Rodriguez said it has met since 2002. In 2007, that filing will come from R348, the recently-identified lead compound in Rigel's JAK3 kinase inhibitor program. A Phase I trial in rheumatoid arthritis is slated to begin this year, with a trial in psoriasis on deck.

And Rigel is planning for 2008 as well, when it expects to file an IND with an AXL kinase inhibitor for solid tumors and endometriosis. Positive data in animal models of oncology with lead compounds from the program were presented at the American Association for Cancer Research meeting last month, where Rodriguez said they generated a "really high level of interest."

He also pointed to data presented earlier this year with an anti-HIV candidate from Rigel's preclinical ubiquitin ligase program, an emerging field he defined as "where kinases were 10 years ago." All of Rigel's compounds are generated internally. "We've been very successful in discovering novel products," Rodriguez said.

So successful, in fact, that Rigel lends its discovery prowess to partners such as Janssen Pharmaceutica NV, Novartis Pharma AG, Daiichi Pharmaceuticals Co. Ltd., and Merck & Co. Inc. Rigel also out-licensed its aurora kinase inhibitor program, now in Phase I for cancer, to Merck Serono SA and its preclinical inhaled SYK kinase inhibitor program to Pfizer Inc. (See BioWorld Today, Jan. 21, 2005, and Oct. 26, 2005.)

As for R788 and R348, Rodriguez said Rigel will not partner them in the near term, instead planning to carry them "through Phase II" and into Phase III. But some of the earlier-stage programs are up for grabs. Rodriguez said Rigel is "speaking to partners" about a JAK2 program for myeloproliferative disorders and other cancers, as well as other programs.