Prosecution Insights
Last updated: April 19, 2026
Application No. 18/015,041

WATER SOLUBLE PRODRUGS OF PTBA FOR USE IN HDAC INHIBITION AND ENHANCING RENAL RECOVERY FOLLOWING ACUTE KIDNEY INJURY

Non-Final OA §103§112
Filed
Jan 06, 2023
Examiner
KIFLE, BRUCK
Art Unit
1624
Tech Center
1600 — Biotechnology & Organic Chemistry
Assignee
Klotho Therapeutics Inc.
OA Round
1 (Non-Final)
79%
Grant Probability
Favorable
1-2
OA Rounds
2y 0m
To Grant
95%
With Interview

Examiner Intelligence

Grants 79% — above average
79%
Career Allow Rate
1356 granted / 1712 resolved
+19.2% vs TC avg
Strong +16% interview lift
Without
With
+15.9%
Interview Lift
resolved cases with interview
Fast prosecutor
2y 0m
Avg Prosecution
27 currently pending
Career history
1739
Total Applications
across all art units

Statute-Specific Performance

§101
0.9%
-39.1% vs TC avg
§103
12.2%
-27.8% vs TC avg
§102
13.0%
-27.0% vs TC avg
§112
53.7%
+13.7% vs TC avg
Black line = Tech Center average estimate • Based on career data from 1712 resolved cases

Office Action

§103 §112
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 . Election/Restrictions Applicant's election with traverse of “A compound, or prodrug of 4-(phenylthio)butanoic acid (PTBA) according to Formula I: PNG media_image1.png 159 242 media_image1.png Greyscale or a stereoisomer, tautomer or pharmaceutically acceptable salt thereof, wherein: R1 is O; and R2 is selected from the group consisting of: 1-(N,N-dimethyl)ethanamine, 1-(1-methyl-N,N-dimethyl)ethanamine, or 1-(N,N,N-trimethyl) ethanamine” in the reply filed on October 28, 2025 is acknowledged. Since this is not an election of a species and because the definition of R2 is selected from compounds, and not a substituent, a telephone call was made to Mr. Charles Meeker on November 7, 2025 to request clarification and an election of species. Mr. Meeker indicated that Compound 22 in Table 1 (page 19) is the elected species. In this species R1 is O and R2 is Cl-N+(CH3)3-CH2-CH2-. The elected species has the following structural formula RN 2757686-92-1 CAPLUS CN Ethanaminium, N,N,N-trimethyl-2-[1-oxo-4-(phenylthio)butoxy]-, chloride (1:1) (CA INDEX NAME) PNG media_image2.png 198 438 media_image2.png Greyscale . The traversal is on the ground(s) that the compounds have the same property. In addition, Applicants argue the patentability of the claimed compounds, which is not on point here. This is not found persuasive because the common structural feature is known as indicated in the previous office action. In fact, claim 1, for example, is anticipated by the prior art compound in Fig 1, second row, second compound, (or same compound in page 20) in WO 2012/109527. The claims lack unity of invention because compounds of formula (I) do not possess single structural element that is shared by all of the alternatives. The common structural feature shared by all of the alternatives of formula (I), is old. The common structural feature of formula I, is not a patentable advance over the prior art. The special technical feature is defined as meaning those technical features that define the contribution which each claimed invention, considered as a whole, makes over the prior art. The feature is, thus, not special if it is known. That what is common here is known. The claims are drawn to structurally dissimilar compounds which are classified separately, require separate literature searches and are not art recognized equivalents. They are made and used independently. The groups embraced at R2-R1- are so diverse in scope that a serious burden exists to search the application as a whole. Therefore, restriction to a specific core is required. Each group at R2-R1- supports a different patent. For example, considering a tiny subset of groups embraced by R2-R1-, a compound having piperidine-O- is classified separately from a compound having HOOC-NH- at R2-R1- or a compound having alkoxy or aminoalkyl. These examples indicate the serious burden placed on the office. A reasonable search of the entire genus could not be conducted without undue burden. If, say a compound having HOOC-NH- were anticipated at R2-R1-, applicants would not acquiesce in the rejection of, say, a piperidine-O- thereover or vice-versa. They are patentably distinct. The search required for any one of R2-R1- is not required for another. The elected species was not found but is not allowable because a compound which renders it obvious was found in the search. The search was expanded according to MPEP 803.02 to embrace compounds of formula I wherein R2-R1- represents alkylaminoalkoxy, i.e., R2 represents alkylamino R2 represents O. Subject matter not embraced by the group indicated as being examined from the remaining claims are withdrawn from consideration as being drawn to non-elected subject matter because art was found. Note that compounds, corresponding compositions, a method of use and a process of making that are of the same scope are considered to form a single inventive concept. The requirement is still deemed proper and is therefore made FINAL. Applicants are advised of MPEP 803.02 Restriction - Markush Claims [R - 2], fourth and fifth paragraph, where is stated: “As an example, in the case of an application with a Markush - type claim drawn to the compound C - R, wherein R is a radical selected from the group consisting of A, B, C, D, and E, the examiner may require a provisional election of a single species, CA, CB, CC, CD, or CE. The Markush - type claim would then be examined fully with respect to the elected species and any species considered to be clearly unpatentable over the elected species. If on examination the elected species is found to be anticipated or rendered obvious by prior art, the Markush - type claim and claims to the elected species shall be rejected, and claims to the non - elected species would be held withdrawn from further consideration. As in the prevailing practice, a second action on the rejected claims would be made final.” (emphasis added). On the other hand, should no prior art be found that anticipates or renders obvious the elected species, the search of the Markush-type claim will be extended. If prior art is found that anticipates or renders obvious the Markush-type claim with respect to a non-elected species, the Markush-type claim shall be rejected and claims to the nonelected species held withdrawn from further consideration. The prior art search, however, will not be extended unnecessarily to cover all nonelected species. Should applicant, in response to this rejection of the Markush-type claim, overcome the rejection, as by amending the Markush-type claim to exclude the species anticipated or rendered obvious by the prior art, the amended Markush-type claim will be reexamined. The prior art search will be extended to the extent necessary to determine patentability of the Markush-type claim. In the event prior art is found during the reexamination that anticipates or renders obvious the amended Markush-type claim, the claim will be rejected and the action made final. Amendments submitted after the final rejection further restricting the scope of the claim may be denied entry. Claim Rejections - 35 USC § 112 The following is a quotation of 35 U.S.C. 112(b): (b) CONCLUSION.—The specification shall conclude with one or more claims particularly pointing out and distinctly claiming the subject matter which the inventor or a joint inventor regards as the invention. The following is a quotation of 35 U.S.C. 112 (pre-AIA ), second paragraph: The specification shall conclude with one or more claims particularly pointing out and distinctly claiming the subject matter which the applicant regards as his invention. Claims 1-14 are rejected under 35 U.S.C. 112(b) or 35 U.S.C. 112 (pre-AIA ), second paragraph, as being indefinite for failing to particularly point out and distinctly claim the subject matter which the inventor or a joint inventor (or for applications subject to pre-AIA 35 U.S.C. 112, the applicant), regards as the invention. i) The phrase “or prodrug of 4-(phenylthio)butanoic acid” in claim 1 is unclear. The phrase “A compound of Formula I” along with the structural formula and definition of the variables fully defines the compound. The compound of the formula I is not limited to 4-(phenylthio)butanoic acid. In addition, the prodrug of 4-(phenylthio)butanoic acid is not known because arriving at a given prodrug requires research. It is improper to require research for the skilled artisan to understand what the prodrug of 4-(phenylthio)butanoic acid looks like. ii) The term “substituted” without saying which substituents are intended is indefinite. One skilled in the art cannot say which substituents are permitted and which ones are not. iii) The substituents throughout the claims have been presented as compounds. These do not have open valencies and, therefore, no point of attachment to the rest of the molecule. Appropriate correction throughout the claims is required. For example, 1-(N,N,N-trimethyl) ethanamine is the compound (without a counter ion) N+(CH3)3-CH2-CH3. The corresponding group when the point of attachment is at the ethylene would be the group 1-(N,N,N-trimethylamino) ethylene with the intended counter ion. Similarly, alkanolamine is a compound. Depending on the intended point of attachment, the group could be hydroxalkylyamino (HO-alk-NH-) or alkylaminoalkoxy (HN(alk)alk-O-) or hydroxyamino (HO-NH-) or hydroxy alkyl amino (OH-N(alk)-. Another example is “amide.” The group -C(O)-NH2 is carboxamido. See also, ether, ester, aldehyde, etc. That is, a compound is not a substituent. Applicants need to go through the claims and rewrite the intended groups because these are open to different interpretations. iii) The claims have not been presented using proper US practice. Thus, the terms “preferably,” “more preferably” and “still more preferably” render the claims indefinite. It is unclear whether the preferred embodiments limit the claim or not. The metes and bounds of the claim should be clearly set forth. iv) The groups “heterocyclic” and “heterocycloalkyl” are indefinite because it is not known how many atoms make up the ring, which atoms are present and what kind of a ring (monocyclic, bicyclic, spiro, fused, bridged, saturated, etc.) is intended. v) Claim 2 is defined by what R2 is not. It is unclear how this claim limits claim 1. For example, R2 is not permitted to be H in claim 1. Also, the claim includes a broad group (e.g., alkyl) followed by a narrower term, This a range-within-a-range and renders the claim indefinite. vi) The structural formula in claim 7 are unclear. Appropriate correction is required. See also claim 12. vii) The compound of claim 13 is named “Formula I” but is different from “Formula I” in claim 1. These different compounds need to be named differently (e.g., Formula I’). 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. Claims 1-11 and 13-14 are rejected under 35 U.S.C. 103 as being unpatentable over Belhir et al. (Reactive & Functional Polymers (2016), 101, 82-89). The reference teaches the compound depicted below in page 84, top of Figure 1. RN 1884262-68-3 CAPLUS CN Ethanaminium, N,N,N-trimethyl-2-[1-oxo-3-(phenylthio)propoxy]-, chloride (1:1) (CA INDEX NAME) PNG media_image3.png 163 398 media_image3.png Greyscale . The elected species differs from this prior art compound by the length of the linking carbon chain between the S and C(O). The elected species has a C3 linking carbon chain over the C2 linking chain of the prior art. It has been long established that structural relationship varying the size of a linking carbon chain - is per se obvious. Specifically, In re Shetty, 195 USPQ 753, In re Wilder, 195 USPQ 426 and Ex Parte Greshem 121 USPQ 422 all feature a compound with a C2 link rejected over a compound with a C1 link. Similarly, In re Chupp, 2 USPQ 2nd 1437 and In re Coes, 81 USPQ 369 have a C1 link unpatentable over a C2 link. Ex parte Ruddy 121 USPQ 427 has a C3 link unpatentable over a C1 link. Ex parte Nathan, 121 USPQ 349 found the insertion of a C2H4 link obvious. In all of these cases, the variation was per-se obvious and did not require a specific teaching. Similarly, Claims 1-11 and 13-14 are rejected under 35 U.S.C. 103 as being unpatentable over Tsatsas et al. (Journal of Medicinal Chemistry (1971), 14(10), 1004-5). The reference teaches structurally similar compounds that differ by having a C1 linker over claimed C3 linker. See Abstract. Copious amount of art was found that render obvious the claims because they differ only by the length of the linking carbon chain for the search that embraced compounds of formula I wherein R1 is O and R2 is alkyl substituted by an amine. The search was not further expanded. Any inquiry concerning this communication or earlier communications from the examiner should be directed to BRUCK KIFLE whose telephone number is (571)272-0668. The examiner can normally be reached 8 AM - 6 PM, M-F. 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, Jeffrey H. Murray can be reached at 571-272-9023. 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. November 15, 2025 /BRUCK KIFLE/Primary Examiner, Art Unit 1624
Read full office action

Prosecution Timeline

Jan 06, 2023
Application Filed
Nov 15, 2025
Non-Final Rejection — §103, §112 (current)

Precedent Cases

Applications granted by this same examiner with similar technology

Patent 12600732
BIFUNCTIONAL COMPOUNDS FOR DEGRADING BTK VIA UBIQUITIN PROTEOSOME PATHWAY
2y 5m to grant Granted Apr 14, 2026
Patent 12595238
PROCESS FOR PRODUCING HEXAHYDRO 1,3,5-TRINITRO-1,3,5-TRIAZINE AND OCTAHYDRO-1,3,5,7-TETRANITRO-1,3,5,7-TETRAZOCINE
2y 5m to grant Granted Apr 07, 2026
Patent 12583863
SYNTHETICALLY MODIFIABLE ION CHANNELS
2y 5m to grant Granted Mar 24, 2026
Patent 12577239
NOVEL SULFILIMINES OR SULFOXIMINES CONTAINING FUNGICIDAL HETEROCYCLIC COMPOUNDS
2y 5m to grant Granted Mar 17, 2026
Patent 12566113
REVERSIBLE FIXING REAGENTS AND METHODS OF USE THEREOF
2y 5m to grant Granted Mar 03, 2026
Study what changed to get past this examiner. Based on 5 most recent grants.

AI Strategy Recommendation

Get an AI-powered prosecution strategy using examiner precedents, rejection analysis, and claim mapping.
Powered by AI — typically takes 5-10 seconds

Prosecution Projections

1-2
Expected OA Rounds
79%
Grant Probability
95%
With Interview (+15.9%)
2y 0m
Median Time to Grant
Low
PTA Risk
Based on 1712 resolved cases by this examiner. Grant probability derived from career allow rate.

Sign in with your work email

Enter your email to receive a magic link. No password needed.

Personal email addresses (Gmail, Yahoo, etc.) are not accepted.

Free tier: 3 strategy analyses per month