ANTISENSE: Isis Advances on Multiple Fronts - ISIS Pharmaceuticals Inc - Brief Article

Applied Genetics News, Dec 19, 1999

A number of developments have occurred recently with regard to antisense compounds developed by Isis Pharmaceuticals (ISIP). The company announced that it will initiate phase III trials of ISIS 3521. On the down side, the company

will discontinue development of ISIS 2302 for rheumatoid arthritis based on phase II data. Isis has recently received $120 million in financing to support the commercialization both ISIS 3521 for cancer indications and ISIS 2302 for Crohn's disease.

Also, company researchers published a report in Nature Biotechnology concerning the control of Bcl-xS expression using antisense oligo nucleotides. Finally, Isis announced the issuance of its 450th patent involving antisense technology. ISIS 3521 is an antisense inhibitor of protein kinase C-alpha (PKC-alpha) expression. PKC-alpha is a member of a multi-gene family of signal transduction proteins that regulate information flow in and out of cells and modulate cellular responses to environmental stimuli. PKC-alpha has been implicated in the growth of a range of solid tumors.

Isis Pharmaceuticals recently released results of phase I/II clinical trials ISIS 3521 for patients with non-small cell lung cancer. Results from the trial to date show that of 15 patients with non-small cell lung cancer, 13 have benefited from the drug through objective responses or stable disease lasting from more than 2 months to more than 13 months thus far. Eight of the 15 (53%) patients have experienced partial responses.

To date, survival results from the study show that 7/15 (47%) patients have lived 1 year or more with the longest survival at 21 months following study entry. After an average of 8 months of follow-up, 90% of the patients are alive and continuing to be evaluated.

"We are pleased with the continued safety profile of the drug and remain confident that ISIS 3521 could play a valuable role when used in combination with standard chemotherapies to treat this disease," says F. Andrew Dorr, M.D. vice president of drug development at Isis. "We feel that these data support our decision to move into phase III trials of ISIS 3521 in non-small cell lung cancer."

Isis has also conducted small-scale clinical trials using ISIS 3521 as a single agent treatment for ovarian cancer and non- Hodgkin's lymphoma. Novartis Pharma Ag, however, has discontinued its participation as a partner in the development of ISIS 3521 and another compound, ISIS 5132.

Isis presented results of its randomized, double-blind, placebo controlled phase II trial of its antisense oligonucleotide, ISIS 2302, to treat longstanding, refractory rheumatoid arthritis at American College of Rheumatology's 63rd Annual Scientific Meeting held in Boston. ISIS 2302 is an inhibitor of the expression of ICAM-1, an intercellular adhesion molecule that is central in up- regulation of the inflammatory system.

ISIS 2302 (32 patients) or placebo (11 patients) was administered every other day intravenously for 1 month, with patient follow-up for 6 months. Using standard efficacy measures (Paulus 20 criteria) and grouping all 3 dosing groups (0.5, 1.0 and 2.0 mg/kg), ISIS 2302 patients displayed moderate improvements compared to placebo (25% vs. 10%) in months 4 to 6 on this study. A greater fraction of patients treated with ISIS 2302 experienced marked improvement (19% ISIS 2302 vs. 0% placebo treated patients reaching Paulus 50 responses during the trial). No significant side effects reported.

However, because the benefit was not observed until month four after dosing was initiated and because the drug must be given intravenously, it is not as attractive as new therapies currently on the market. Isis has decided not to pursue development on ISIS 2302 for RA and is planning to conduct trials of a second- generation, orally active antisense drug for RA in the future.

Isis scientists successfully used an antisense oligonucleotide to both increase and decrease the levels of two functionally antagonistic proteins encoded by the Bcl-x gene, one of which is involved in the development of resistance in human tumors to chemotherapeutic agents.

The Nature Biotechnology paper reporting these results is entitled "Induction of endogenous Bcl-xS through the control of Bcl-x pre mRNA splicing by antisense nucleotides" and is authored by Jennifer Taylor, Qing Qing Zhang, Jacqueline Wyatt, and Nicholas Dean, all of Isis Pharmaceuticals.

Research has shown that alternatively spliced RNA produced from a single gene (Bcl-x gene) produces two proteins (Bcl-xS and Bcl-xL) with opposite functions. Bcl-xS is a promoter of apoptosis, and Bcl-xL is an anti-apoptotic protein. Isis researchers found that by targeting a second generation methoxyethyl (MOE) antisense inhibitor, to pre-mRNA from the bcl-x gene, they were able to drive the RNA splicing from one form of Bcl-x to the other. This resulted in a decrease in the Bcl-xL and an increase in Bcl-xS levels in human cancer cell lines. This action, in turn, sensitized cancer cells to apoptotic stimuli and to the cytotoxic effects of chemotherapeutic drugs, therefore increasing their therapeutic effect.