A summary judgment issued Wednesday by the U.S. DistrictCourt in Delaware found that Liposome Technology Inc.'s (LTI)patent on a method of preparing amphotericin-B-containingliposomes is not infringed by Vestar Inc.'s AmBisome.
The court's opinion, handed down the day before the summaryjudgment, stated that LTI's patent does not apply to liposomesthat do not change substantially in size distribution duringsuspension. According to Vestar of San Dimas, Calif., AmBisomeis "size stable."
LTI of Menlo Park, Calif., said Thursday that it will appeal thedecision.
In stipulations mutually agreed upon by both parties in thesummary judgment, LTI will not attempt to prove that Vestarinfringes its patent as interpreted by the district court. Vestar,in turn, has dropped its claim that the LTI patent is invalid. LTIwill appeal the district court's interpretation of its patent,however, claiming that it applies more broadly to includeliposomes that do change substantially in size distributionduring suspension. Vestar has agreed that if the patent isinterpreted as such on appeal, it will not claim that it does notinfringe the LTI patent.
The stipulations were made to avoid a trial based on the court'sinterpretation of the LTI patent, Peter Leigh, LTI's vicepresident and chief financial officer, told BioWorld. Heindicated that a final resolution of the case would be reachedmore quickly by moving directly to an appeal.
Vestar filed suit against LTI the day after LTI's patent on thestorage of amphotericin-B-containing liposomes issued inJanuary 1993. Vestar claimed that LTI's patent is invalid,unenforceable and not infringed by AmBisome. LTI filed itscountersuit against Vestar last March.
AmBisome is approved in eight European countries for thetreatment of severe fungal infections, Hart said, and isavailable in more than a dozen others on a named-patientbasis. LTI's anti-fungal, Amphocil, was approved in the UnitedKingdom last August, although the launch of the product hasbeen delayed as the company re-evaluates some of its clinicaldata.
Neither company has a U.S.-approved product. Vestar'sAmBisome is being developed by Fujisawa U.S. in the U.S.,where it's in Phase II clinicals, Hart said. LTI's Amphocil is inPhase III U.S. and European clinical trials, said Leigh, addingthat the company hopes to file an new drug approvalapplication (NDA) with the FDA for the product before the endof 1994.
Vestar is also involved in similar litigation with The LiposomeCompany Inc., which claimed in a June 1992 suit that Vestar isinfringing its lyophilization patent. Vestar countersued thePrinceton, N.J., company in July 1992, claiming that thecompany's patent is invalid. That case was argued in November1993 in Delaware District Court. Both parties are now preparingpost-trial briefs before a decision is handed down, Hart said.
Another suit continues between LTI and Vestar in Europe.Vestar claims that LTI's liposome formulated anti-cancer drugDoxil (doxorubicin-containing liposomes) infringes its Europeanpatent on tumor targeting.
Vestar's stock (NASDAQ:VSTR) closed on Thursday at $6.88, up38 cents. LTI's stock (NASDAQ:LTIZ) rose $1.13 per share,closing at $18.75.
-- Karl A. Thiel Associate Editor
(c) 1997 American Health Consultants. All rights reserved.