Prosecution Insights
Last updated: April 19, 2026
Application No. 17/802,588

FORMULATION BASED ON POLYHEXAMETHYLENE BIGUANIDE FOR USE IN THE TREATMENT OF ACANTHAMOEBA KERATITIS AND/OR FUNGAL INFECTIONS

Final Rejection §103
Filed
Aug 26, 2022
Examiner
FAY, ZOHREH ALEMZADEH
Art Unit
1617
Tech Center
1600 — Biotechnology & Organic Chemistry
Assignee
Sifi S P A
OA Round
2 (Final)
52%
Grant Probability
Moderate
3-4
OA Rounds
3y 2m
To Grant
45%
With Interview

Examiner Intelligence

Grants 52% of resolved cases
52%
Career Allow Rate
563 granted / 1094 resolved
-8.5% vs TC avg
Minimal -7% lift
Without
With
+-6.7%
Interview Lift
resolved cases with interview
Typical timeline
3y 2m
Avg Prosecution
67 currently pending
Career history
1161
Total Applications
across all art units

Statute-Specific Performance

§101
2.2%
-37.8% vs TC avg
§103
50.7%
+10.7% vs TC avg
§102
12.0%
-28.0% vs TC avg
§112
20.2%
-19.8% vs TC avg
Black line = Tech Center average estimate • Based on career data from 1094 resolved cases

Office Action

§103
Notice of Pre-AIA or AIA Status The present application, filed on or after March 16, 2013, is being examined under the first inventor to file provisions of the AIA . Claims 1-20 are presented for examination. The amendments and remarks filed on 11/04/2025 have been received and entered. Claim Rejections - 35 USC § 103 The following is a quotation of 35 U.S.C. 103 which forms the basis for all obviousness rejections set forth in this Office action: A patent for a claimed invention may not be obtained, notwithstanding that the claimed invention is not identically disclosed as set forth in section 102, if the differences between the claimed invention and the prior art are such that the claimed invention as a whole would have been obvious before the effective filing date of the claimed invention to a person having ordinary skill in the art to which the claimed invention pertains. Patentability shall not be negated by the manner in which the invention was made. The factual inquiries for establishing a background for determining obviousness under 35 U.S.C. 103 are summarized as follows: 1. Determining the scope and contents of the prior art. 2. Ascertaining the differences between the prior art and the claims at issue. 3. Resolving the level of ordinary skill in the pertinent art. 4. Considering objective evidence present in the application indicating obviousness or nonobviousness. This application currently names joint inventors. In considering patentability of the claims the examiner presumes that the subject matter of the various claims was commonly owned as of the effective filing date of the claimed invention(s) absent any evidence to the contrary. Applicant is advised of the obligation under 37 CFR 1.56 to point out the inventor and effective filing dates of each claim that was not commonly owned as of the effective filing date of the later invention in order for the examiner to consider the applicability of 35 U.S.C. 102(b)(2)(C) for any potential 35 U.S.C. 102(a)(2) prior art against the later invention. Claim(s) 1-20 is/are rejected under 35 U.S.C. 103 as being unpatentable over Wang et al. (US 20070140897) in view of Yu et al. (US 20050196370) and further in view of Borazjani et al. (EP 1852133 Submitted by the applicant). Wang et al. teach an ophthalmic acceptable composition for use in the ocular region of a patient, the ophthalmic acceptable composition comprising water, a biguanide containing antimicrobial agent and a pH adjusting agent to adjust the pH to a minimum of 4 and a maximum of 6. The invention further comprises administering the ophthalmic acceptable composition to the eye of a patient in need of treatment. See the abstract. Wang et al. teach that biguanide antimicrobial agents have been used to preserve ophthalmic solutions and demonstrate relatively low toxicity in ocular tissues. Biguanide antimicrobial agents include polyhexamethylene biguanide, chlorhexidine and Alexidine. See Para [0008]. Wang et al. teach that To effectively preserve an ophthalmic composition, sufficient preservative is necessary to prevent growth of S. aureus, P. aeruginosa and E. coli bacteria and C. albicans and A. Niger fungi over the shelf life of the product. Typically, a clinically effective formulation will contain the lowest amount of a preservative required to accomplish the desired effect. Between 0.5 ppm and 3.0 ppm of a biguanide has been used to preserve most ophthalmic solutions. See Para [0009]. The use of polyhexamethylene biguanide and/or chlorhexidine for treatment of Acanthamoeba keratitis and Fungal keratitis is taught in Para [0013]. Wang et al. teach that the amount of antimicrobial agent in the ophthalmic composition is a maximum of about 1 ppm and a minimum of about 0.1 wt. %. T typically, the amount of antimicrobial agent in the multipurpose solution is a minimum of about 4.5 ppm, about 5 ppm, about 10 ppm, about 15 ppm or about 20 ppm. Typically, the amount of antimicrobial agent in the ophthalmic solution is a maximum of about 1000 ppm, about 500 ppm, about 300 ppm, about 100 ppm, about 75 ppm or about 50 ppm. See Para [0037]. Wang et al. teach that one or more penetration enhancers will generally be utilized in a minimum amount of about 0.01 weight percent and/or a maximum of about 10 wt. %. See Para [0039]. Wang et al. teach examples of stabilizers that are effective in an aqueous solution include but are not limited to ophthalmic acceptable antioxidants (ascorbate, methionine, citric acid, BHT), complexing agents (cyclodextrin and derivatives, hyaluronic acid, citric acid), non-ionic surfactants (poloxamers such as Tetronics. RTM. 908, tyloxapol) and chelating agents and salts thereof (hydroxyl alkyl phosphonate, sodium edentate). See Para [0041]. The concentrations of stabilizers is taught to be about 0.001 wt. %, about 0.005 wt. %, about 0.01 wt. % and/or a maximum amount of about 0.5 wt. %, about 0.3 wt. %, about 0.1 wt. %, about 0.08 wt. %, about 0.05 wt. %, about 0.03 wt. %, about 0.01 wt. %. See Para [0043]. Wang et al. teach the viscosity enhancing agents include natural polysaccharides and gums, such as alginate, carrageenan, guar, karaya, locust bean, tragacanth agarose and xanthan; modified naturally occurring polymers such as carboxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, methylcellulose, hydroxypropylmethyl guar and carboxymethyl guar, synthetic polymers, such as carboxy vinyl polymers, polyvinyl alcohol and polyvinyl pyrrolidone. See Para [0050]. Wang et al. teach Suitable buffers include, but not limited to, acetate buffer, citrate buffer, formate buffer, histidine, succinate buffer, phosphate buffer, maleate buffer, propionate buffer, malate buffer, pyridine buffer, piperazine buffer, cacodylate buffer, MES buffer, bis-tris buffer, carbonate buffer, imidazole buffer, ADA buffer, ACES buffer, PIPES buffer, MOPSO buffer, HEPES buffer, MOPS buffer, BES buffer, triethanolamine buffer, triethanolamine buffer and borate buffer. Generally, buffers will be used in amounts ranging from about 0.05 to about 2.5 weight percent, and preferably, from about 0.1 to about 1.5 weight percent. See Para [0054], claim 22 and claim 45. The 0.9 percent solution of sodium chloride as a tonicity agents is taught in Para [0056]. Wang et al. teach that Preferably, the tonicity agent is employed in an amount to provide a final osmotic value that is a minimum of 200 mOsm/kg, 220 mOsm/kg and/or a maximum of about 450 mOsm/kg, 350 mOsm/kg or about 320 mOsm/kg. See Para [0056]. The use of an eye drop is taught in Para [0061]. The treatment of Aspergillus keratitis is taught in Para [0016]. The treatment of Fusarium keratomycosis is taught in Para [0017]. Wang differs from the claimed invention in specifically teaching the addition of benzalkonium chloride and the molecular weight of polyhexamethylene biguanide. Yu et al. teach that the addition of chlorhexidine and benzalkonium chloride to polyhexamethylene biguanide in ophthalmic formulations as old and well known. See claim 9. Borazjani et al. teach an ophthalmic composition that exhibits enhanced biocidal efficacy against acanthamoeba relative to a reference ophthalmic solution that does not contain the polycationic compound. See the abstract. the use of polyhexamethylene biguanide is taught in claim 7. The molecular weight of PHMB is taught to be up to 100,000, which overlaps or encompassed the claimed molecular weight. Mixing and filtering the claimed ingredients taught by the prior art does not create a patentably distinct process of making an ophthalmic solution in the absence of evidence to the contrary. The determination of polydispersity index and concentrations are considered to be within the skill of the artisan. Applicant's attention is drawn to In Re Aller, 220 F.2d 454, 456, 105 USPQ 233, 235 (CCPA 1955), wherein the court stated that "Generally, differences in concentration or temperature will not support the patentability of subject matter encompassed by the prior art unless there is evidence indicating such concentration or temperature is critical. "[W]here the general conditions of a claim are disclosed in the prior art, it is not inventive to discover the optimum or workable ranges by routine experimentation". Applicant has presented no evidence to the unexpected and unobvious nature of the claimed invention, and as such, claims 1-20 are properly rejected under 35 U.S.C. 103 (a). Response to Arguments Applicant’s arguments have been noted. Applicant in his remarks argues that “applicant points out that Wang et al. do not teach the role of the molecular weight of PHMB and polydispersity index of the polymer to provide a better stability and efficacy of the composition against ocular infection. Moreover, in order to improve penetration of the active ingredient, the Wang formulation discusses including a viscosifier as penetration enhancer, in a concentration ranging from 0.001 wt. % to 5 wt. %. This is a different solution to the posed technical problem”. It is the examiner’s position that presented data in the specification to show the advantages of the claimed molecular weight are not commensurate in scope with the claimed language. The data use one concentration within the scope of the claimed molecular weight. However the claims are not drawn to one concentration. Furthermore, the newly relied upon reference teaches the molecular weight encompassing or overlap the claimed molecular weight. The addition of a viscosity enhancing agents in wang, reads on the claimed invention, which uses the Phrase “comprising”, which permits for the addition of other ingredients. Applicant in his remarks further argues that “As for Yu et al., the reference is not properly applied here, where it is directed to an oil-in-water emulsion for the treatment of dry eye. One skilled in the art would have no incentive or motivation to use this formulation for the treatment of Acanthamoeba keratitis. As such, it is not properly combined with Wang et al”. It is the examiner’s position that Yu was relied upon to show that the addition of chlorhexidine and benzalkonium chloride to polyhexamethylene biguanide in ophthalmic formulations as old and well known. furthermore, the newly relied upon teaches the use of quaternary ammonium compounds in a composition being used for treating acanthamoeba keratitis. The remaining arguments regarding the CN patent have not been addressed, since such reference is not relied upon in the instant Office action. Applicant's submission of an information disclosure statement under 37 CFR 1.97(c) with the timing fee set forth in 37 CFR 1.17(p) on 05/03/2025 prompted the new ground(s) of rejection presented in this Office action. Accordingly, THIS ACTION IS MADE FINAL. See MPEP § 609.04(b). Applicant is reminded of the extension of time policy as set forth in 37 CFR 1.136(a). A shortened statutory period for reply to this final action is set to expire THREE MONTHS from the mailing date of this action. In the event a first reply is filed within TWO MONTHS of the mailing date of this final action and the advisory action is not mailed until after the end of the THREE-MONTH shortened statutory period, then the shortened statutory period will expire on the date the advisory action is mailed, and any nonprovisional extension fee (37 CFR 1.17(a)) pursuant to 37 CFR 1.136(a) will be calculated from the mailing date of the advisory action. In no event, however, will the statutory period for reply expire later than SIX MONTHS from the mailing date of this final action. Any inquiry concerning this communication or earlier communications from the examiner should be directed to ZOHREH A FAY whose telephone number is (703)756-1800. The examiner can normally be reached Monday-Friday 9:30AM-6:00. Examiner interviews are available via telephone, in-person, and video conferencing using a USPTO supplied web-based collaboration tool. To schedule an interview, applicant is encouraged to use the USPTO Automated Interview Request (AIR) at http://www.uspto.gov/interviewpractice. If attempts to reach the examiner by telephone are unsuccessful, the examiner’s supervisor, Sue Liu can be reached at 571-272-5539. The fax phone number for the organization where this application or proceeding is assigned is 571-273-8300. Information regarding the status of published or unpublished applications may be obtained from Patent Center. Unpublished application information in Patent Center is available to registered users. To file and manage patent submissions in Patent Center, visit: https://patentcenter.uspto.gov. Visit https://www.uspto.gov/patents/apply/patent-center for more information about Patent Center and https://www.uspto.gov/patents/docx for information about filing in DOCX format. For additional questions, contact the Electronic Business Center (EBC) at 866-217-9197 (toll-free). If you would like assistance from a USPTO Customer Service Representative, call 800-786-9199 (IN USA OR CANADA) or 571-272-1000. /ZOHREH A FAY/Primary Examiner, Art Unit 1617
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Prosecution Timeline

Aug 26, 2022
Application Filed
Oct 24, 2024
Response after Non-Final Action
May 01, 2025
Non-Final Rejection — §103
Nov 04, 2025
Response Filed
Jan 31, 2026
Final Rejection — §103 (current)

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Study what changed to get past this examiner. Based on 5 most recent grants.

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Prosecution Projections

3-4
Expected OA Rounds
52%
Grant Probability
45%
With Interview (-6.7%)
3y 2m
Median Time to Grant
Moderate
PTA Risk
Based on 1094 resolved cases by this examiner. Grant probability derived from career allow rate.

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