The PTAB (Patent Trial and Appeal Board) denied a petition to
institute an Inter Partes Review (IPR2016-01608) against Genentech’s U.S. Patent No. 6,716,602, which claims a method for
increasing the product yield of a properly folded polypeptide of interest
produced by recombinant host cells:
1. A method for
increasing the product yield of a properly folded polypeptide of interest
produced by recombinant host cells, wherein expression of the polypeptide by
the recombinant host cells is regulated by an inducible system, which method
comprises
(a) culturing the
recombinant host cells under conditions of high metabolic growth rate; and
(b) reducing the
metabolic rate of the cultured recombinant host cells at the time of induction
of polypeptide expression, wherein reducing the metabolic rate comprises
reducing the feed rate of a carbon/energy source, or reducing the amount of
available oxygen, or both, and wherein the reduction in metabolic rate result
in increase yield of properly folded polypeptide.
The Petitioner (bioeq IP AG) relied on Seeger (17
Enzyme & Microbial Tech. 947–53 (1995)), in which cells were grown at 30°C
in a fed-batch procedure, with a predetermined exponential feeding rate to
ensure constant specific growth rates. Seeger explains that product formation
was induced by shifting either the temperature from 30°C to 42°C, or by adding
isopropyl-ß-D-thiogalacto-pyranoside (IPTG). Seeger observes acetic acid
accumulation in response to temperature-induced product expression. To prevent
that accumulation, the exponential feeding rate was reduced after the temperature shift to 42°C. Seeger determined that the temperature-induced
production of bFGF (basic fibroblast growth factor) “generated
more total and more soluble bFGF compared to IPTG-induced cultures.”
The
PTAB disagreed that Seeger anticipated claim 1 since it did not teach reduction
of metabolic rate. In particular, “Petitioner
relies upon the disclosure of the ’602 patent describing reducing metabolic
rate in cells already in a reduced growth state by reducing the rates of oxygen
uptake and the corresponding rates of uptake of a carbon/energy source. However,
Petitioner has not addressed adequately how Seeger’s method of inducing
expression by increasing temperature from 30 to 42°C may have affected the
metabolic rate.”
Petitioner
relied only on Seeger for anticipation of claim 1, and did not have a back-up
obviousness position.
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