MPEP 2138.05
"Reduction to Practice"

Ninth Edition of the MPEP, Revision 10.2019, Last Revised in June 2020

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2138.05    "Reduction to Practice" [R-10.2019]

[Editor Note: This MPEP section has limited applicability to applications subject to examination under the first inventor to file (FITF) provisions of the AIA as set forth in 35 U.S.C. 100 (note). See MPEP § 2159 et seq. to determine whether an application is subject to examination under the FITF provisions, MPEP § 2159.03 for the conditions under which this section applies to an AIA application, and MPEP § 2150 et seq. for examination of applications subject to those provisions.]

Reduction to practice may be an actual reduction or a constructive reduction to practice which occurs when a patent application on the claimed invention is filed. The filing of a patent application serves as conception and constructive reduction to practice of the subject matter described in the application. Thus the inventor need not provide evidence of either conception or actual reduction to practice when relying on the content of the patent application. Hyatt v. Boone, 146 F.3d 1348, 1352, 47 USPQ2d 1128, 1130 (Fed. Cir. 1998). A reduction to practice can be done by another on behalf of the inventor. De Solms v. Schoenwald, 15 USPQ2d 1507, 1510 (Bd. Pat. App. & Inter. 1990). "While the filing of the original application theoretically constituted a constructive reduction to practice at the time, the subsequent abandonment of that application also resulted in an abandonment of the benefit of that filing as a constructive reduction to practice. The filing of the original application is, however, evidence of conception of the invention." In re Costello, 717 F.2d 1346, 1350, 219 USPQ 389, 392 (Fed. Cir. 1983)(The second application was not co-pending with the original application and it did not reference the original application. Because of the requirements of 35 U.S.C. 120 had not been satisfied, the filing of the original application was not recognized as constructive reduction to practice of the invention.).


When a party to an interference seeks the benefit of an earlier-filed U.S. patent application, the earlier application must meet the requirements of 35 U.S.C. 120 and 35 U.S.C. 112(a) or pre-AIA 35 U.S.C. 112, first paragraph for the subject matter of the count. The earlier application must meet the enablement requirement and must contain a written description of the subject matter of the interference count. Hyatt v. Boone, 146 F.3d 1348, 1352, 47 USPQ2d 1128, 1130 (Fed. Cir. 1998). Proof of a constructive reduction to practice requires sufficient disclosure under the "how to use" and "how to make" requirements of 35 U.S.C. 112(a) or pre-AIA 35 U.S.C. 112, first paragraph. Kawai v. Metlesics, 480 F.2d 880, 886, 178 USPQ 158, 163 (CCPA 1973) (A constructive reduction to practice is not proven unless the specification discloses a practical utility where one would not be obvious. Prior art which disclosed an anticonvulsant compound which differed from the claimed compound only in the absence of a -CH2- group connecting two functional groups was not sufficient to establish utility of the claimed compound because the compounds were not so closely related that they could be presumed to have the same utility.). The purpose of the written description requirement is "to ensure that the inventor had possession, as of the filing date of the application relied on, of the specific subject matter later claimed by him." In re Edwards, 568 F.2d 1349, 1351-52, 196 USPQ 465, 467 (CCPA 1978). The written description must include all of the limitations of the interference count, or the applicant must show that any absent text is necessarily comprehended in the description provided and would have been so understood at the time the patent application was filed. Furthermore, the written description must be sufficient, when the entire specification is considered, such that the "necessary and only reasonable construction" that would be given it by a person skilled in the art is one that clearly supports each positive limitation in the count. Hyatt v. Boone, 146 F.3d at 1354-55, 47 USPQ2d at 1130-1132 (Fed. Cir. 1998) (The claim could be read as describing subject matter other than that of the count and thus did not establish that the applicant was in possession of the invention of the count.). See also Bigham v. Godtfredsen, 857 F.2d 1415, 1417, 8 USPQ2d 1266, 1268 (Fed. Cir. 1988) ("[t]he generic term halogen comprehends a limited number of species, and ordinarily constitutes a sufficient written description of the common halogen species," except where the halogen species are patentably distinct).


"In an interference proceeding, a party seeking to establish an actual reduction to practice must satisfy a two-prong test: (1) the party constructed an embodiment or performed a process that met every element of the interference count, and (2) the embodiment or process operated for its intended purpose." Eaton v. Evans, 204 F.3d 1094, 1097, 53 USPQ2d 1696, 1698 (Fed. Cir. 2000).

The same evidence sufficient for a constructive reduction to practice may be insufficient to establish an actual reduction to practice, which requires a showing of the invention in a physical or tangible form that shows every element of the count. Wetmore v. Quick, 536 F.2d 937, 942, 190 USPQ 223, 227 (CCPA 1976). For an actual reduction to practice, the invention must have been sufficiently tested to demonstrate that it will work for its intended purpose, but it need not be in a commercially satisfactory stage of development. See, e.g., Scott v. Finney, 34 F.3d 1058, 1062, 32 USPQ2d 1115, 1118-19 (Fed. Cir. 1994) (citing numerous cases wherein the character of the testing necessary to support an actual reduction to practice varied with the complexity of the invention and the problem it solved). If a device is so simple, and its purpose and efficacy so obvious, construction alone is sufficient to demonstrate workability. King Instrument Corp. v. Otari Corp., 767 F.2d 853, 860, 226 USPQ 402, 407 (Fed. Cir. 1985).

For additional cases pertaining to the requirements necessary to establish actual reduction to practice see DSL Dynamic Sciences, Ltd. v. Union Switch & Signal, Inc., 928 F.2d 1122, 1126, 18 USPQ2d 1152, 1155 (Fed. Cir. 1991) ("events occurring after an alleged actual reduction to practice can call into question whether reduction to practice has in fact occurred"); Fitzgerald v. Arbib, 268 F.2d 763, 765-66, 122 USPQ 530, 531-32 (CCPA 1959) ("the reduction to practice of a three-dimensional design invention requires the production of an article embodying that design" in "other than a mere drawing"); Birmingham v. Randall, 171 F.2d 957, 80 USPQ 371, 372 (CCPA 1948) (To establish an actual reduction to practice of an invention directed to a method of making a product, it is not enough to show that the method was performed. "[S]uch an invention is not reduced to practice until it is established that the product made by the process is satisfactory, and [ ] this may require successful testing of the product.").


"The nature of testing which is required to establish a reduction to practice depends on the particular facts of each case, especially the nature of the invention." Gellert v. Wanberg, 495 F.2d 779, 783, 181 USPQ 648, 652 (CCPA 1974) ("an invention may be tested sufficiently … where less than all of the conditions of actual use are duplicated by the tests"); Wells v. Fremont, 177 USPQ 22, 24-5 (Bd. Pat. Inter. 1972) ("even where tests are conducted under ‘bench’ or laboratory conditions, those conditions must ‘fully duplicate each and every condition of actual use’ or if they do not, then the evidence must establish a relationship between the subject matter, the test condition and the intended functional setting of the invention," but it is not required that all the conditions of all actual uses be duplicated, such as rain, snow, mud, dust and submersion in water).


The invention must be recognized and appreciated for a reduction to practice to occur. "The rule that conception and reduction to practice cannot be established nunc pro tunc simply requires that in order for an experiment to constitute an actual reduction to practice, there must have been contemporaneous appreciation of the invention at issue by the inventor…. Subsequent testing or later recognition may not be used to show that a party had contemporaneous appreciation of the invention. However, evidence of subsequent testing may be admitted for the purpose of showing that an embodiment was produced and that it met the limitations of the count." Cooper v. Goldfarb, 154 F.3d 1321, 1331, 47 USPQ2d 1896, 1904 (Fed. Cir. 1998) (citations omitted). Meitzner v. Corte, 537 F.2d 524, 528, 190 USPQ 407, 410 (CCPA 1976) (there can be no conception or reduction to practice of a new form or of a process using such a new form of an otherwise old composition where there has been no recognition or appreciation of the existence of the new form); Estee Lauder, Inc. v. L’Oreal S.A., 129 F.3d 588, 593, 44 USPQ2d 1610, 1615 (Fed. Cir. 1997) ("[W]hen testing is necessary to establish utility, there must be recognition and appreciation that the tests were successful for reduction to practice to occur." A showing that testing was completed before the critical date, and that testing ultimately proved successful, was held insufficient to establish a reduction to practice before the critical date, since the success of the testing was not appreciated or recognized until after the critical date.); Parker v. Frilette, 462 F.2d 544, 547, 174 USPQ 321, 324 (CCPA 1972) ("[an] inventor need not understand precisely why his invention works in order to achieve an actual reduction to practice").


"Inurement involves a claim by an inventor that, as a matter of law, the acts of another person should accrue to the benefit of the inventor." Cooper v. Goldfarb, 154 F.3d 1321, 1331, 47 USPQ2d 1896, 1904 (Fed. Cir. 1998). Before a non-inventor’s recognition of the utility of the invention can inure to the benefit of the inventor, the following three-prong test must be met: (1) the inventor must have conceived of the invention, (2) the inventor must have had an expectation that the embodiment tested would work for the intended purpose of the invention, and (3) the inventor must have submitted the embodiment for testing for the intended purpose of the invention. Genentech, Inc. v. Chiron Corp., 220 F.3d 1345, 1354, 55 USPQ2d 1636, 1643 (Fed. Cir. 2000). In Genentech, a non-inventor hired by the inventors to test yeast samples for the presence of the fusion protein encoded by the DNA construct of the invention recognized the growth-enhancing property of the fusion protein, but did not communicate this recognition to the inventors. The court found that because the inventors did not submit the samples for testing growth-promoting activity, the intended purpose of the invention, the third prong was not satisfied and the uncommunicated recognition of the activity of the fusion protein by the non-inventor did not inure to the benefit of the inventor. See also Cooper v. Goldfarb, 240 F.3d 1378, 1385, 57 USPQ2d 1990, 1995 (Fed. Cir. 2001) (Cooper sent to Goldfarb samples of a material for use in vascular grafts. At the time the samples were sent, Cooper was unaware of the importance of the fibril length of the material. Cooper did not at any time later convey to, or request from, Goldfarb any information regarding fibril length. Therefore, Goldfarb’s determination of the fibril lengths of the material could not inure to Cooper’s benefit.).


The device reduced to practice must include every limitation of the count. Fredkin v. Irasek, 397 F.2d 342, 158 USPQ 280, 285 (CCPA 1968); every limitation in a count is material and must be proved to establish an actual reduction to practice. Meitzner v. Corte, 537 F.2d 524, 528, 190 USPQ 407, 410 (CCPA 1976). See also Hull v. Bonis, 214 USPQ 731, 734 (Bd. Pat. Inter. 1982) (no doctrine of equivalents—remedy is a preliminary motion to amend the count to conform to the proofs).


Utility for the invention must be known at the time of the reduction to practice. Wiesner v. Weigert, 666 F.2d 582, 588, 212 USPQ 721, 726 (CCPA 1981) (except for plant and design inventions); Azar v. Burns, 188 USPQ 601, 604 (Bd. Pat. Inter. 1975) (a composition and a method cannot be actually reduced to practice unless the composition and the product produced by the method have a practical utility); Ciric v. Flanigen, 511 F.2d 1182, 1185, 185 USPQ 103, 105-6 (CCPA 1975) ("when a count does not recite any particular utility, evidence establishing a substantial utility for any purpose is sufficient to prove a reduction to practice"; "the demonstrated similarity of ion exchange and adsorptive properties between the newly discovered zeolites and known crystalline zeolites … have established utility for the zeolites of the count"); Engelhardt v. Judd, 369 F.2d 408, 411, 151 USPQ 732, 735 (CCPA 1966) (When considering an actual reduction to practice as a bar to patentability for claims to compounds, it is sufficient to successfully demonstrate utility of the compounds in animals for somewhat different pharmaceutical purposes than those asserted in the specification for humans.); Rey-Bellet v. Engelhardt, 493 F.2d 1380, 1384, 181 USPQ 453, 455 (CCPA 1974) (Two categories of tests on laboratory animals have been considered adequate to show utility and reduction to practice: first, tests carried out to prove utility in humans where there is a satisfactory correlation between humans and animals, and second, tests carried out to prove utility for treating animals.).


A probable utility does not establish a practical utility, which is established by actual testing or where the utility can be "foretold with certainty." Bindra v. Kelly, 206 USPQ 570, 575 (Bd. Pat. Inter. 1979) (Reduction to practice was not established for an intermediate useful in the preparation of a second intermediate with a known utility in the preparation of a pharmaceutical. The record established there was a high degree of probability of a successful preparation because one skilled in the art may have been motivated, in the sense of 35 U.S.C. 103, to prepare the second intermediate from the first intermediate. However, a strong probability of utility is not sufficient to establish practical utility.); Wu v. Jucker, 167 USPQ 467, 472 (Bd. Pat. Inter. 1968) (screening test where there was an indication of possible utility is insufficient to establish practical utility). But see Nelson v. Bowler, 628 F.2d 853, 858, 206 USPQ 881, 885 (CCPA 1980) (Relevant evidence is judged as a whole for its persuasiveness in linking observed properties to suggested uses. Reasonable correlation between the two is sufficient for an actual reduction to practice.).