By Donald Zuhn --
Last week, StemCells, Inc. announced that the U.S. Patent and Trademark Office had issued Notices of Intent to Issue Ex Parte Reexamination Certificates with respect to the Palo Alto-based biotech company's U.S. Patent Nos. 5,851,832 and 6,497,872. The '832 patent, entitled "In vitro growth and proliferation of multipotent neural stem cells and their progeny," is directed to a method for preparing a population of mammalian neural cells enriched with multipotent neural stem cells. The '872 patent, entitled "Neural transplantation using proliferated multipotent neural stem cells and their progeny," is directed to a method of transplanting multipotent neural stem cell progeny into a host.
In its statement, StemCells contended that the USPTO had upheld the patents, which the company exclusively licenses, "with only minor amendments, thereby rejecting the arguments raised by Neuralstem, Inc. in its reexamination petitions of last year." StemCells noted that the '832 and '872 patents are two of four patents that StemCells asserted in a 2006 patent infringement suit against Neuralstem, Inc. of Rockville, MD.
In response, Neuralstem filed a Request for Ex Parte Reexamination in April 2007 for each of the asserted patents. On April 1, 2008, the Patent Office issued a Notice of Intent to Issue an Ex Parte Reexamination Certificate in Reexamination No. 90/008,581, which concerned the '872 patent, and on April 9th, the Office issued a Notice of Intent in Reexamination No. 90/008,580, which concerned the '832 patent.
StemCells President and CEO Martin McGlynn stated that the Patent Office's issuance of the Notices of Intent "preserves intact the basis of [StemCells'] infringement action against Neuralstem,” adding that, "the Patent Office has reconfirmed the ground-breaking nature of the inventions claimed in these patents, which are part of our multi-layered patent portfolio." Mr. McGlynn predicted that the Office would issue similar decisions on the remaining two patents, allowing StemCells to "move ahead expeditiously" with its suit against Neuralstem.
In response to StemCells' announcement, Neuralstem released a statement of its own. According to Neuralstem's release, StemCells "completely mischaracterized the meaning of the US Patent and Trademark Office's most recent action." Neuralstem President and CEO Richard Garr asserted that in order to secure the Notices of Intent, StemCells was forced to make "numerous substantial amendments," and that these amendments "completely destroy any basis for [StemCells'] assertions of infringement by Neuralstem." Mr. Garr added that "any attempt by [StemCells] to reopen their baseless law suit will be unsuccessful [since] Neuralstem does not infringe upon any of their 'old' claims, nor do we infringe upon any of the significantly modified claims that they salvaged in the reexamination process."
Claim 1 of the '832 patent, as issued on December 22, 1998, reads:
1. A method for preparing a population of mammalian neural cells enriched with multipotent neural stem cells comprising:
(a) obtaining a population of mammalian neural cells which contains at least one multipotent neural stem cell capable of producing progeny that are capable of differentiating into neurons and glia, including astrocytes;
(b) preparing a culture medium containing one or more predetermined growth factors capable of inducing multipotent neural stem cell proliferation; and
(c) combining the population of mammalian neural cells obtained in (a) with the culture medium prepared in (b) and culturing said mammalian neural cells under conditions that allow the proliferation of said at least one multipotent neural stem cell to produce multipotent neural stem cell progeny which includes daughter multipotent neural stem cells to produce a cell culture that contains a percentage of multipotent neural stem cells that is at least ten fold higher than that of said population of mammalian neural cells obtained in (a).
In the Statement of Reasons for Patentability, the Examiner noted that claim 1 was patentable in view of the patentee's amendments to recite "non-immortalized, human neural cells" rather than "mammalian neural cells" in step (a), "serum free culture media" instead of "culture media" in step (b), and "undifferentiated multipotent neural stem cell progeny" rather than "multipotent neural stem cell progeny" in step (c). Similar amendments were made to other claims that were at issue.
Claim 1 of the '872 patent, as issued on December 24, 2002, reads:
1. A method of transplanting multipotent neural stem cell progeny to a host comprising:
(a) obtaining a population of cells derived from mammalian neural tissue containing at least one multipotent CNS neural stem cell, said neural stem cell under suitable culture conditions producing progeny that differentiate into neurons that express neuron specific enolase or neurofilament and glia that express glial fibrillary acidic protein or express galactocerebroside;
(b) culturing the neural stem cell in (a) in a culture medium containing one or more growth factors which under suitable culture conditions induces multipotent neural stem cell proliferation;
(c) inducing proliferation of said multipotent neural stem cell to produce neural stem cell progeny which includes multipotent neural stem cell progeny cells; and
(d) transplanting said multipotent neural stem cell progeny to said host.
In the '581 reexamination, the Examiner noted that claim 1 was patentable in view of the patentee's amendments to recite "a human host" instead of a "host" as well as, inter alia, the recitation of "human neural tissue" instead of "mammalian neural tissue" in step (a), "serum-free culture medium" instead of "culture medium" in step (b), and "undifferentiated human neural stem cell progeny" rather than "neural stem cell progeny" in step (c).
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