Invalidity dossier
US 4956288
Method for producing cells containing stably integrated foreign DNA at a high copy number, the cells produced by this method, and the use of these cells to produce the polypeptides coded for by the foreign DNA
Current assignee: BTG International Inc
Added 9/23/2026, 9:21:31 PM
Active provider: DeepSeek · deepseek-flash
Patent summary
Title, assignee, inventors, filing/issue dates, abstract, and a plain-language overview of the claims.
US4956288A — Concise Overview
Title: "Method for producing cells containing stably integrated foreign DNA at a high copy number, the cells produced by this method, and the use of these cells to produce the polypeptides coded for by the foreign DNA."
Patent number / application: US4956288A; application US07/185,212.
Inventor: James G. Barsoum.
Assignee: Original assignee Biogen Inc. (later reassigned to Biogen N.V., then Biogen, Inc.; the source lists BTG International Inc. as current assignee). Per your instructions, I do not analyze ownership transfers.
Key dates (from the supplied source): Priority/filing date 1988-04-22; publication/grant 1990-09-11; anticipated expiration 2008-04-22; status listed as Expired – Lifetime.
Purpose: The invention provides an improved method, employing electroporation, for producing recombinant host cells characterized by stably integrated foreign DNA at high copy number, useful for efficient large-scale production of recombinant proteins and polypeptides. The source notes that product yield depends on copy number, transcription efficiency, and translation efficiency.
Plain-language scope: An initial cell population is electroporated with foreign DNA comprising (i) a "product gene" coding for a desired polypeptide, (ii) a "protective gene" whose protein protects the cell against a toxic substance (or against loss of a previously essential nutrient), with higher copy numbers needed for higher toxin concentrations, and optionally (iii) a "selective gene" where one copy per cell suffices for protection. After culturing for recovery and integration, cells are exposed to sufficiently high toxic-substance concentrations (or sufficiently low nutrient) to kill or severely retard low-copy-number cells. The invention also includes cells produced by this process and their use to produce the encoded polypeptides.
What the excerpt does not establish: It does not provide complete claims, the full specification, examples, or data; figures are only partially reproduced (FIG. 1 vector pSV2-DHFR; FIG. 2 truncated). It does not establish validity, enforceability, or the legal effect of assignments/status, and omits details of litigation and prior art.
Source: https://patents.google.com/patent/[US4956288](/patent/US4956288)/en
Generated 10/1/2026, 9:34:21 PM
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PTAB challenges
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Assignment history
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Prior art
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Obviousness
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Extensions
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Derivative works
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