By Brady Huggett

Enzon Inc. and partner Schering-Plough Corp. didn¿t see conclusive noninferior data in their PEG-Intron for injection vs. Intron A for injection Phase III trial in patients with newly diagnosed chronic myelogenous leukemia.

PEG-Intron was administered once weekly and demonstrated clinical comparability to Intron A given daily, as well as showing a comparable safety profile. However, the efficacy results did not meet the primary endpoint of noninferiority. The major cytogenetic response rates at month 12 for both products were similar to those previously reported for alpha interferon.

Overall, however, this miss doesn¿t sully what most view to be a valuable product.

¿I don¿t think this means a lot,¿ said Matt Geller, an analyst for CIBC World Markets Corp. in New York. ¿I think the response is overdone. This is a small indication and they didn¿t put a lot of money or patients into it. They aren¿t trying to prove that it¿s better, that¿s the key. If it was a superiority claim they wanted, then they might have a problem.

¿The hepatitis data look great,¿ he added, pointing to the indication the product was approved for in January. (See BioWorld Today, Jan. 23, 2001.)

In a research note, CIBC and Geller predicted PEG-Intron would bring in $729 million in end-user sales for fiscal year 2002. The products costs more than twice as much as Intron A.

Indeed, the response on the Street was minimally negative. Enzon¿s stock (NASDAQ:ENZN) fell $5.41 Monday, or about 7 percent, to close at $69.98 on a day when most biotech stocks fell. Schering-Plough¿s stock (NYSE:SGP) dipped $1.03, closing at $41.31.

Kenneth Zuerblis, chief financial officer and vice president, finance, at Piscataway, N.J.-based Enzon, said the onus of CML decision making is Schering-Plough¿s. Data from the trial are not yet publicly available, but Zuerblis said Schering would publish the data at the American Society of Hematology meeting in November.

¿Schering is continuing to evaluate if they can file off this data or not,¿ Zuerblis said. ¿They basically showed it was comparable once a week as opposed to seven times a week. But this is a small piece of Schering-Plough¿s ongoing clinical trials. It¿s not expected to be a significant driver of revenue. The main driver is hepatitis C.¿

Zuerblis said about 3,000 to 4,000 patients are diagnosed with CML per year in the United States.

PEG-Intron is a longer-acting form of Madison, N.J.-based Schering-Plough¿s Intron A. The companies began their collaboration in 1990 and the product uses Enzon¿s polyethylene glycol technology to achieve the longer duration. The hepatitis C approval remains its potential blockbuster indication, but Schering-Plough has ongoing trials in larger oncology indications that will eventually determine PEG-Intron¿s worth, Zuerblis said.

¿We still view the results of the trial as positive in their own right because once-a-week PEG-Intron was comparative to daily injections,¿ he said. ¿And that¿s just part of a larger PEG-Intron franchise, which is driven by hepatitis C.¿

Enzon has other products in its pipeline. It has Prothecan, a PEG-enhanced version of a small molecule called camptothecin, an anticancer compound. The product is a topoisomerase 1 inhibitor and is about to start Phase II trials, Zuerblis said. It also has a PEG version of paclitaxel that is in Phase I trials.

Already approved, Enzon has Oncaspar for acute lymphoblastic leukemia and Adagen for a form of severe combined immunodeficiency disease referred to as ¿Bubble Boy¿ disease. Those two products generated $15 million in sales in 2000, Zuerblis said.

Enzon and Schering-Plough have filed for PEG-Intron/ribavirin combination therapy to back up the single-agent use already approved to treat hepatitis C. An FDA action letter is expected in August.

What happens to PEG-Intron concerning chronic myeloid leukemia remains to be seen. But with the hepatitis C approval and trials ongoing, Geller suggested taking a step back to view PEG-Intron.

¿This is clearly a major product with a major launch coming up and one needs to focus on the bigger picture,¿ he said.

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