Onyx Pharmaceuticals, the U.S. com­pany developing car­filz­o­mib as a potential new treat­ment for multiple myeloma, announced earlier today that the U.S. Food and Drug Administration (FDA) has granted "standard review designation" to the com­pany's New Drug Applica­tion for car­filz­o­mib.

This means that the FDA expects to make a decision by July 27, 2012, on Onyx's application to market carfilzomib ^[1] (Kyprolis ^[2]) in the United States.

The announcement is a disappointment for Onyx, which had hoped to receive a so-called "priority review" of the car­filz­o­mib application.

The target FDA review time for applications granted a priority review is four months shorter than for drugs with a standard review designation.

If the FDA makes a positive decision regarding car­filz­o­mib's new drug application by the end of next July, Onyx will be allowed to start marketing the drug in the United States as a new treat­ment for re­lapsed and refractory myeloma.

A negative decision by the FDA would delay the launch of car­filz­o­mib until Onyx is able to address any questions or concerns raised by the FDA.

In its press release ^[3] about the FDA standard review designation, Onyx explained that the FDA decided on a standard review for at least two reasons.

First, the FDA said that its advisory committee of outside oncology experts increasingly is recommending that the FDA not grant priority review unless a new drug application is based on a Phase 3 clinical trial.

This is not the case with the car­filz­o­mib application, which is based on data from a Phase 2 trial.  Phase 2 trials are smaller than Phase 3 clinical trials, and they are often not as scientifically rigorous as Phase 3 trials.

Second, Onyx said that "the FDA outlined potential review issues including whether the application is sufficient to support an FDA conclusion that the data provided within the [New Drug Application] meets accelerated approval criteria and whether the benefit and risk are appropriately balanced, given that the application is based on a single-arm study."

The statement that "the FDA outlined potential review issues" will be of concern to those hoping for an FDA approval of car­filz­o­mib by next July.

The statement could be interpreted as meaning the FDA has broader concerns about the car­filz­o­mib application -- not just concerns about granting the application priority review.

Onyx has scheduled a conference call for Monday morning at 8:00 a.m. Eastern Time to discuss the FDA decision.

Until car­filz­o­mib receives FDA approval, the drug is available through Onyx’s expanded access pro­gram ^[4] for re­lapsed and refractory myeloma patients in the U.S. who do not have any other treat­ment options.

Carfilzomib works similarly to the existing multiple myeloma treat­ment Velcade ^[5] (bor­tez­o­mib) by preventing the breakdown of protein in cancer cells, triggering their death.

Along with pomalidomide ^[6] – a chemical relative of multiple myeloma drugs Revlimid ^[7] and thalidomide ^[8] (Thalomid) – car­filz­o­mib is considered one of the most promising new myeloma treat­ments that could be approved by the FDA in the next few years.