In a final written decision, the Patent Trial and Appeal Board (PTAB) cancelled claims 1 and 2 of MiMedx’s U.S. Patent No. 8,372,437 directed to a product-by-process for producing placental tissue grafts. Claim 1, which is representative, recited (i) isolating intact amnion and chorion layers from placental tissue, (ii) washing the two layers, (iii) laminating the two layers together, and (iv) dehydrating the laminated graft.
In its response to the petition for inter partes review, MiMedx argued that the combination of references cited by the petitioner taught away from the claimed invention. Specifically, MiMedx argued that a person of ordinary skill in the art would not have retained the amnion and/or the chorion layers when creating a placental tissue graft because one of the asserted references, Sulner, taught substantial removal of cells (and therefore the two claimed layers) from a graft. This “decellularization” procedure was believed to have reduced immunogenicity and thus reduced rejection rates. MiMedx, thus, argued that Sulner “taught away” because a person of ordinary skill would not have isolated and retained the amnion and/or chorion layers based on any combination of references involving Sulner.
The PTAB found MiMedx’s arguments unpersuasive. The PTAB acknowledged that Sulner taught “decellularization,” but that this disclosure did not amount to a “teaching away” because the first asserted reference, Klen, disclosed retaining the cellular material in placental grafts. The PTAB explained that the test for obviousness is what the combined teachings of the references would have suggested to those of ordinary skill in the art. According to the PTAB, a person of ordinary skill in the art would have retained the amnion and chorion layers because Klen taught that its cellularized grafts may be used in the treatment of burns, in treating skin defects caused by leprosy, in ophthalmology at burns of the cornea, and in varicose ulcers. The PTAB also rejected MiMedx’s argument that it was “conventional wisdom” to decellularize placental grafts because the specification did not include any discussion of decellularization. The PTAB, thus, found that the specification of the ’437 patent itself did not support the patent owner’s argument that the lack of a decellularization went against conventional wisdom.
Musculoskeletal Transplant Found. v. MiMedx Grp., Inc., Case IPR2015-00664, Paper No. 49, (PTAB, Aug. 16, 2016) [Green (opinion), Paulraj, and Harlow].