ImmunoGen cancer treatment application gets another chance

ImmunoGen has been given the go-ahead to revive its patent application for a cancer treatment dosage following a Federal Circuit ruling on Friday.

A three-judge panel for the US Court of Appeal for the Federal Circuit vacated a lower court's decision ruling an ImmunoGen patent application as “factually indefinite” and obvious, claiming it made a “fatal error” in its judgment.

The circuit vacated the US District Court for the Eastern District of Virginia’s decision to grant a summary judgment and remanded the case for proceedings consistent with its opinion.

The patent application (US application number 14/509,809) covers an “adjusted ideal body weight (AIBW)” which dictates the ideal dosage for mirvetuximab soravtansine (IMGN853), a promising cancer treatment, to avoid ocular side effects.

Although neither the examiner nor the board of the US Patent and Trademark Office (USPTO) initially rejected the claims of the ‘809 application for indefiniteness, the USPTO argued that the term “AIBW” is indefinite.

The district court agreed with this and concluded that the ‘809 application failed to define “AIBW” or “IBW” “in such a way that a skilled artisan would be informed” about the scope of the invention.

It claimed that ImmunoGen’s usage of the phrase “for example” in the language proceeding the AIBW formula “made it clear that there were multiple ways to calculate AIBW”, which would leave a skilled artisan to “guess” whether the formula provided is the only one that is covered by the ‘809 application.

“Our review of the evidence, however, reveals that the underlying material factual findings are far from undisputed,” said the Federal Circuit.

The circuit disagreed that the application did not provide a “limiting or defining” guidance on the calculation of AIBW and its ruling that ‘809 disclosed multiple formulas for calculating AIBW.

Instead, the Federal Circuit sided with ImmunoGen and held that the ‘809 application is drawn to a specific dosing regime.

It also held that the USPTO never disputed the definiteness, nor gave an indication that it failed to understand the meaning of the “indefinite term”.

As a result, the Federal Circuit concluded that: “there are still disputed questions of material fact and summary judgment is therefore inappropriate.”

On the issue of obviousness, the district court ruled that prior art taught “every element” of the pending claims of the ‘809 application.

However, the Federal Circuit said: “In reaching this conclusion, the district court improperly resolved a number of factual findings against ImmunoGen.”

The circuit held that the district court erred in granting a summary judgment on the matter and vacated the decision that the terms were indefinite and would be obvious and remanded the case.

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