Prior art

US patent 12221638, titled "Method for producing recombinant hyaluronidase," was filed on August 6, 2021, and published on February 11, 2025. It claims priority from Korean Patent Application No. 10-2020-0099100, filed on August 7, 2020. The patent describes a method for producing hyaluronidase PH20 or variants thereof with improved enzymatic activity and productivity by controlling N-glycosylation levels under specific culture conditions, including controlled glucose concentration and a decreased culture temperature for a specific period.

Here's an analysis of the most relevant prior art cited in US patent 12221638:

1. US Patent No. 9,447,401

• Full Citation: U.S. Pat. No. 9,447,401.
• Publication/Filing Date: The full text of US12221638 mentions this patent in the context of human-derived "hyaluronidase PH20" or "PH20 variant" being exemplified. While the exact filing/publication dates for US9447401 aren't directly provided in the text of US12221638, US12221638's priority date is August 7, 2020. Therefore, US9447401 would have a publication date prior to this.
• Brief Description: US12221638 states that US9447401 exemplifies human-derived hyaluronidase PH20 or PH20 variants, which include substitutions, deletions, and insertions of one or more amino acid residues, and optionally truncations of N-terminal and/or C-terminal amino acid residues, while retaining hyaluronidase enzymatic activity.
• Potential Anticipation: This patent potentially anticipates claims related to the basic structure and function of hyaluronidase PH20 variants. Specifically, it could be relevant to claims that broadly define the hyaluronidase PH20 protein or its variants, such as those that describe the enzyme itself rather than the specific production method. Claims 1, 2, and any other claims that broadly define the recombinant hyaluronidase PH20 or its variants, particularly the sialylation, galactosylation, and mannosylation contents, could be at least partially anticipated if US9447401 discloses hyaluronidase PH20 with N-glycan characteristics falling within the ranges claimed in US12221638.

2. International Patent Publication No. 2020/022791

• Full Citation: International Patent Publication No. 2020/022791.
• Publication/Filing Date: The full text of US12221638 mentions this international publication in the same context as US9447401, referring to it as exemplifying human-derived "hyaluronidase PH20" or "PH20 variant." The publication number itself indicates a publication year of 2020. Since US12221638 claims priority to a Korean application filed on August 7, 2020, International Patent Publication No. 2020/022791 would have a publication date on or before this date to be considered prior art.
• Brief Description: Similar to US9447401, this international publication is cited in US12221638 as exemplifying human-derived hyaluronidase PH20 or variants with amino acid modifications and hyaluronidase activity.
• Potential Anticipation: This international patent publication also potentially anticipates claims related to the composition of hyaluronidase PH20 variants, particularly if it describes such variants with N-glycan profiles or enzymatic activities similar to those claimed in US12221638. Claims related to the recombinant hyaluronidase PH20 or its variants and their N-glycan characteristics (sialylation, galactosylation, mannosylation) could be potentially anticipated.

3. Arming et al., "In vitro mutagenesis of PH-20 hyaluronidase from human sperm", Eur. J. Biochem, 1997, pp. 810-814, vol. 247.

• Full Citation: Arming, S., et al., "In vitro mutagenesis of PH-20 hyaluronidase from human sperm", Eur. J. Biochem, 1997, pp. 810-814, vol. 247.
• Publication Date: 1997.
• Brief Description: This reference is cited in US12221638 as having "revealed that an arginine residue having positive charges in hyaluronidase PH20 is essential for enzymatic activity for binding to hyaluronic acid, which is a substrate having a large amount of negative charges distributed therein".
• Potential Anticipation: This publication provides foundational knowledge about the enzymatic activity of PH20 hyaluronidase and the role of specific amino acid residues. While it focuses on in vitro mutagenesis and the mechanism of activity, it could potentially anticipate claims that generally describe the enzymatic activity of hyaluronidase PH20 or its variants, especially if such claims do not specifically tie the activity to the novel production methods or specific N-glycan profiles of US12221638. It might anticipate aspects of the problem definition or the general understanding of hyaluronidase function, but less likely the specific method claims or the resulting glycan profiles.

4. Bookbinder et al., 2006

• Full Citation: Bookbinder et al., 2006.
• Publication Date: 2006.
• Brief Description: This reference is cited multiple times in US12221638. It discusses hyaluronidases degrading hyaluronic acid to reduce viscosity and increase tissue permeability, their use in enhancing absorption of body fluids, improving diffusion of local anesthetics, and mentions the recombinant human PH20 protein developed by Halozyme Therapeutics Inc. and sold as "Hylenex."
• Potential Anticipation: This reference provides a general overview of hyaluronidase function, therapeutic uses, and the existence of recombinant human PH20 (Hylenex). It establishes the background knowledge in the field. It could potentially anticipate claims that broadly describe the application or general characteristics of recombinant human PH20. However, it is unlikely to anticipate the specific culture methods, N-glycan profiles, or enhanced activity described in the claims of US12221638, as the patent aims to improve upon existing production methods and resulting protein characteristics.

5. Other General References Cited in the Background
The background section of US12221638 also lists several other academic papers that describe the general state of the art regarding hyaluronidase uses, glycosylation processes, and factors affecting N-glycosylation in cell culture:

• Muchmore et al., 2012
• Krantz et al., 2016
• Clement et al., 2003
• Thomas et al., 2009
• Harb et al., 2010
• Wasserman et al., 2014
• Harris R J et al., 2004
• Schilling, et al., 2002
• Tachibana et al., 1994
• Restelli et al., 2006
• Borys et al., 1993
• Borys et al., 1994
• Clark et al., 2004
• Alan Fersht (1977). Enzyme structure and mechanism

These references contribute to the understanding of the general knowledge base at the time of the invention but are less likely to directly anticipate specific claims of US12221638, which focuses on a novel method for producing hyaluronidase with improved characteristics through specific culture condition manipulation and resulting N-glycan profiles. They establish the technical field and the problems US12221638 seeks to address.

It is important to note that a recent development (May 15, 2026) indicates that the USPTO denied an Inter Partes Review (IPR) petition filed by Halozyme against US Patent No. 12,221,638. Halozyme had argued that Alteogen's "temperature-shift cultivation method" was known in the prior art, but the PTAB found that Halozyme failed to demonstrate a "reasonable likelihood of success" on any of the challenged claims. This suggests that the USPTO considered the prior art cited by Halozyme (which would likely include many of the above) and found it insufficient to invalidate the claims of US12221638.