Guangdong Cell Biotechnology Ltd v. Sudhof

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United States District Court
Northern District of California
UNITED STATES DISTRICT COURT
NORTHERN DISTRICT OF CALIFORNIA
SAN JOSE DIVISION
GUANGDONG CELL
BIOTECHNOLOGY LTD,
Plaintiff,
v.
THOMAS CHRISTIAN SUDHOF,
Defendant.
Case No. 25-cv-08953-VKD
ORDER DIRECTING DEFENDANT TO
SHOW CAUSE WHY FIFTH
COUNTERCLAIM SHOULD NOT BE
STRICKEN
Re: Dkt. No. 50
A party may file an amended pleading once, as a matter of course, “21 days after serving
it,” or “21 days after service of a responsive pleading or 21 days after service of a motion under
Rule 12(b), (e), or (f), whichever is earlier.” Fed. R. Civ. P. 15(a)(1). “In all other cases, a party
may amend its pleading only with the opposing party’s written consent or the court’s leave.” Fed.
R. Civ. P. 15(a)(2).
The Court’s February 25, 2026 case management order set a May 26, 2026 deadline to file
a motion to amend pleadings. See Dkt. No. 30 at 2. On July 20, 2026, the Court granted plaintiff
Guangdong Cell Biotechnology Ltd.’s motion to dismiss defendant Thomas Christian Sudhof’s
counterclaims. Dkt. No. 49. The Court gave Dr. Sudhof limited leave to amend counterclaim 1
(misappropriation of name or likeness), counterclaim 2 (intentional misrepresentation),
counterclaim 3 (negligent misrepresentation), and counterclaim 4 (unfair competition). Id. at 23.
The Court dismissed counterclaim 5 (declaratory relief) without leave to amend. Id. The Court
did not authorize Dr. Sudhof to add new counterclaims.
On August 3, 2026, Dr. Sudhof filed an amended counterclaim that includes a new
counterclaim for breach of contract (counterclaim 5) without obtaining leave to do so. Dkt. No. 50
Case 5:25-cv-08953-VKD Document 51 Filed 08/04/26 Page 1 of 2

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United States District Court
Northern District of California
¶¶ 55-60.
By August 10, 2026, 4:00 p.m., Dr. Sudhof shall file a response to this order, showing
cause why his fifth counterclaim for breach of contract should not be stricken for failure to comply
with Rule 15 and as contrary to the Court’s February 25, 2026 and July 20, 2026 orders.
IT IS SO ORDERED.
Dated: August 4, 2026
Virginia K. DeMarchi
United States Magistrate Judge
Case 5:25-cv-08953-VKD Document 51 Filed 08/04/26 Page 2 of 2