Obviousness

Analysis of Obviousness for U.S. Patent No. 12,168,797

Date of Analysis: 2026-05-13

Patent under Review: U.S. Patent No. 12,168,797, "Signal encoding and decoding in multiplexed biochemical assays" (hereinafter '797 patent).

Assignee: California Institute of Technology

Filing Date: 2023-07-13

I. Introduction and Summary of Invention

The '797 patent is directed to methods, systems, and compositions for the multiplexed detection of a plurality of analytes in a single sample volume. The core of the invention lies in a signal encoding and decoding scheme that allows for the unambiguous identification of the presence or absence of numerous analytes without requiring physical separation, mass spectrometry, or melting curve analysis. This is achieved by encoding each analyte as a unique combination of signal values. In preferred embodiments, these values are different intensities across multiple fluorescence wavelengths (or "colors"). The patent describes non-degenerate coding schemes, including some that are non-degenerate by design, which allow for the deconvolution of a cumulative signal to identify the individual analytes present. Claim 1, for instance, describes a method involving encoding each analyte as a first value (e.g., intensity) and a second value (e.g., wavelength), cumulatively measuring the signal, and determining the presence or absence of each analyte based on the measurement and a non-degenerate coding scheme.

II. Legal Standard for Obviousness under 35 U.S.C. § 103

A claimed invention is unpatentable if the differences between the subject matter sought to be patented and the prior art are such that the subject matter as a whole would have been obvious at the time the invention was made to a person having ordinary skill in the art (POSITA). The analysis of obviousness is based on the four-pronged test laid out in Graham v. John Deere Co., which requires consideration of: (1) the scope and content of the prior art; (2) the differences between the prior art and the claims at issue; (3) the level of ordinary skill in the pertinent art; and (4) secondary considerations of non-obviousness, if any. An obviousness rejection requires a reasoned explanation of why a POSITA would have been motivated to combine the teachings of the prior art references to arrive at the claimed invention with a reasonable expectation of success.

III. Analysis of Potential Obviousness Rejections

Based on a review of the prior art, several combinations of references could be asserted to render the claims of the '797 patent obvious. The primary argument would center on the combination of prior art teaching multiplexed assays using fluorescence detection with prior art disclosing mathematical or signal processing techniques for deconvolution of complex signals.

A. Combination of US 7,741,128 (Chee) and US 6,780,584 (Emonet)

1. Scope and Content of the Prior Art:

   • US 7,741,128 to Chee et al. (Chee): Chee discloses methods for multiplexed nucleic acid analysis using bead-based arrays. Each bead type is associated with a specific probe and is identifiable by a unique fluorescent signature (e.g., a ratio of two or more dyes). This allows for the simultaneous detection of multiple target sequences in a sample. Chee teaches the use of multiple spectrally distinct fluorophores to create these unique signatures for bead identification, and a separate reporter fluorophore to indicate a binding event. While Chee relies on spatially resolved signals (beads), it establishes the principle of using combinations of fluorescent signals to encode identity in a multiplexed assay.
   • US 6,780,584 to Emonet et al. (Emonet): Emonet is directed to methods for analyzing and quantifying the composition of a sample containing multiple fluorescent species without prior separation. Emonet teaches acquiring fluorescence emission spectra at multiple excitation wavelengths and using a matrix-based mathematical deconvolution algorithm (e.g., least-squares analysis) to determine the concentration of each individual fluorescent component in the mixture. This reference provides a clear methodology for resolving a cumulative, spectrally overlapped signal into its constituent parts.

2. Application to the Claims of the '797 Patent:

   • Claim 1 of the '797 patent calls for a method of detecting multiple analytes by: (a) encoding each analyte with a first value (intensity) and a second value (wavelength) to create a non-degenerate coding scheme; (b) contacting a sample with reagents that generate these signals; (c) cumulatively measuring the signals; and (d) determining the presence of analytes from the cumulative measurement.

   • A POSITA would view Chee as disclosing the foundational concept of multiplexed assays where analyte identity is linked to a specific combination of fluorescent signals. The '797 patent's use of different intensities across various colors is an analogous encoding strategy to Chee's use of different dye ratios to encode bead identity. The key difference is that the '797 patent proposes a homogenous, liquid-phase assay, whereas Chee uses a solid support (beads).

   • Emonet provides the missing link for applying Chee's encoding concept to a homogenous assay. Emonet explicitly teaches how to take a cumulative fluorescence signal from a mixture of fluorophores in a solution and mathematically deconvolve it to determine the contribution of each individual fluorophore.

3. Motivation to Combine and Reasonable Expectation of Success:

   • A person of ordinary skill in the art, seeking to develop a higher-throughput, homogenous multiplexed assay (thereby avoiding the complexities of bead-based systems like Chee's), would have been motivated to combine the teachings of Chee and Emonet. The goal of increasing the degree of multiplexing in a single reaction volume was a well-established objective in the field. Applying the deconvolution methods of Emonet to a system where analytes are encoded with unique spectral signatures, a concept taught by Chee, would have been a logical and predictable step.

   • The POSITA would have had a reasonable expectation of success in this combination. Emonet provides the necessary mathematical framework, and Chee demonstrates the feasibility of using combinations of fluorophores for encoding. The application of Emonet's deconvolution algorithms to a set of pre-defined, non-overlapping spectral "codes" (as claimed in the '797 patent) would be a straightforward implementation of the taught principles. The "non-degenerate" coding scheme of the '797 patent would have been an inherent and necessary design choice when implementing such a system to ensure accurate decoding, a principle well understood in information theory and signal processing, and thus an obvious design consideration.

B. Combination of US 2007/0166770 (Winn-Deen) and General Knowledge of Binary or Digital Encoding

1. Scope and Content of the Prior Art:

   • US 2007/0166770 to Winn-Deen et al. (Winn-Deen): Winn-Deen describes methods for quantitative multiplexed PCR using fluorogenic probes (like TaqMan probes). It teaches using different concentrations of probes labeled with the same fluorophore to generate different signal intensities, thereby allowing for the quantification of multiple targets in the same fluorescence channel. This reference directly teaches encoding different analytes (or different concentrations of an analyte) with varying signal intensities within a single color channel.

2. Application to the Claims of the '797 Patent and Motivation to Combine:

   • Winn-Deen discloses the core concept of using multiple, discrete intensity levels within a single fluorescence channel to distinguish between different reactions. The '797 patent expands this concept across multiple color channels. A POSITA, familiar with the standard practice of using multiple color channels in real-time PCR (e.g., for detecting 4-5 different targets, one per color), would have found it obvious to extend Winn-Deen's intensity-based encoding to each of the available color channels to dramatically increase the multiplexing capacity.

   • Furthermore, the specific non-degenerate encoding scheme described in the '797 patent, where analyte codes are assigned values such as 1, 2, 4, 8... in a given channel (as seen in Table 8), is a direct application of a binary or power-of-2 encoding system. This type of encoding is a fundamental concept in computer science and digital signal processing. A POSITA in bioinformatics or a related field would have been well aware of such encoding methods for unambiguously representing information. The motivation would be to create a system where any summed signal has a unique decomposition, which is the exact property provided by a binary or base-2 representation.

   • Therefore, the combination of Winn-Deen's teaching of intensity-based encoding in a single channel with the well-established knowledge of multi-channel fluorescence detection and fundamental digital encoding principles would render the claims of the '797 patent obvious. The combination would be a predictable and logical step for a POSITA aiming to maximize the number of analytes detectable in a standard real-time PCR instrument.

IV. Conclusion

The claims of US Patent No. 12,168,797 are likely obvious under 35 U.S.C. § 103. The invention represents a combination of known elements in the art: (1) multiplexed biochemical assays using fluorescent labels, (2) the concept of encoding analyte identity through combinations of these fluorescent signals, and (3) mathematical deconvolution techniques for resolving cumulative signals. The combination of references such as Chee and Emonet, or Winn-Deen and established principles of digital encoding, would have provided a clear path for a person of ordinary skill in the art to arrive at the claimed invention with a reasonable expectation of success. The key inventive concept—the non-degenerate encoding scheme for a homogenous assay—is either taught by the prior art's signal deconvolution methods or would have been an obvious design choice based on fundamental principles of information theory.