On the ropes for some time now, Genta (NASDAQ:GNTA) may have just received a knockout punch. On Wednesday, an FDA advisory committee voted not to recommend Genta's lead drug, Genasense, for approval (and the FDA generally follows the advice of the advisory panel). Genasense was being considered as a treatment for patients with relapsed or refractory chronic lymphocytic leukemia (CLL). The news has knocked Genta's stock down by nearly two-thirds over the past week.

The past couple of years have been difficult for Genta. In 2004, a similar thumbs-down vote from an advisory panel (regarding the use of a combination therapy of Genasense plus dacarbazine for the treatment of patients with advanced melanoma) prompted Genta to withdraw its new drug application (NDA) with the FDA. May 2005 saw the termination of a development and commercialization agreement with Sanofi-Aventis (NYSE:SNY). Genta has had to initiate follow-on stock offerings in each of the past three years to keep its development programs underway. The company most recently raised just over $40 million in March 2006, largely to support the market release of Genasense, which is now unlikely.

Genasense is an antisense oligonucleotide-based therapy designed to knock down production of Bcl-2, a protein made by cancer cells that is thought to block chemotherapy-induced apoptosis (programmed cell death). Antisense-based therapies have not lived up to the "magic bullet" promise originally bestowed on them in the early '90s, largely because of application issues such as difficulties with systematic delivery in the body. This promise has been shifted of late, as a similar, more potent technology -- RNA interference (RNAi) with siRNAs -- has grabbed the spotlight. Under early stage development by companies like Alnylam Pharmaceuticals (NASDAQ:ALNY) and Sirna Therapeutics (NASDAQ:RNAI), RNAi-based therapies have recently attracted the interest of big pharma. Alnylam has established collaborative agreements with Merck (NYSE:MRK) and Novartis (NYSE:NVS), and Sirna has paired up with GlaxoSmithKline (NYSE:GSK).

Genta may not be counted out quite yet. It has $35 million in cash, which is roughly half the current market value of the company. The company still has a pending review by the European Medicines Agency (EMEA) for the use of Genasense plus dacarbazine for treatment of patients with advanced metastatic melanoma. Genta also markets Ganite for the treatment of cancer-related hypercalcemia. But with more current concerns than promise and a share price well below $1, Genta stock should only be considered by those with a strong appetite for speculation.

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Fool contributor Ralph Casale, known on the discussion boards as HelicalZz, tries to make sense of antisense. He owns shares of Johnson & Johnson, but holds no financial position in any other firm mentioned. The Motley Fool has a disclosure policy.