Obviousness

Obviousness Analysis of US Patent 11,419,823 under 35 U.S.C. § 103

This section analyzes the obviousness of US Patent 11,419,823 based on combinations of prior art references. An invention is obvious if the differences between the claimed invention 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 (POSA). This analysis will identify potential combinations of references and provide a rationale for a POSA's motivation to combine them.

The present invention, US 11,419,823, is directed to stabilized pharmaceutical compositions of tacrolimus, specifically addressing the degradation of tacrolimus into 8-epitacrolimus by incorporating a stabilizing agent, particularly a metal chelating agent or an organic acid, to maintain a pH below 7 in a solid dispersion formulation. The patent also emphasizes sustained-release and low levels of degradation products after storage.

Prior Art References:

The patent itself identifies several relevant prior art documents that disclose tacrolimus-containing pharmaceutical compositions with improved bioavailability and reduced peak-to-trough levels, particularly solid dispersions of tacrolimus in polyethylene glycol (PEG). These include:

• WO2005/020993 (WO '993): Discloses modified release compositions comprising tacrolimus, which may include a solid dispersion or solid solution of tacrolimus in a hydrophilic or water-miscible vehicle. It aims to increase bioavailability and reduce CYP3A4 metabolism.
• WO2005/020994 (WO '994): Discloses pharmaceutical compositions comprising tacrolimus dissolved and/or dispersed in a hydrophilic or water-miscible vehicle to form a solid dispersion or solid solution at ambient temperature, with improved bioavailability.
• WO2008/0145143 (WO '143): Discloses an extended release oral dosage form comprising tacrolimus, emphasizing improved pharmacokinetic parameters.
• WO2010/005980 (WO '980): Discloses tacrolimus-containing pharmaceutical compositions.
• WO2008/084698A1 (WO '698): Discloses a tacrolimus sustained-release pharmaceutical composition comprising a solid dispersion of tacrolimus or a pharmaceutically acceptable salt thereof and a carrier for sustained release.
• WO2007/091109A1 (WO '109): Discloses a pharmaceutical composition comprising tacrolimus in a stable amorphous morphological form, but specifically states it is not in a solid dispersion form.
• "Establishment of new preparation method for solid dispersion formulation of tacrolimus" by YAMASHITA et al. (2003) (Yamashita): Discloses a new method for preparing solid dispersion formulations of tacrolimus using HPMC as a carrier, without dichloromethane, and notes the stability of the formulation after storage at 40°C for 3 months.

Analysis of Obviousness Combinations:

A POSA in the field of pharmaceutical formulation development, around the priority date of US 11,419,823 (May 30, 2008 [cite: US11419823B2 - Google Patents]), would have been aware of the challenges associated with tacrolimus, specifically its poor solubility, low bioavailability, and the desirability of solid dispersion formulations for improved absorption. [cite: US11419823B2 - Google Patents] They would also have recognized the inherent instability of drugs in solid dispersions due to increased molecular exposure, leading to a higher risk of chemical degradation. [cite: US11419823B2 - Google Patents]

Combination 1: WO '993 / WO '994 / WO '143 / WO '980 (or WO '698) + General Knowledge of Pharmaceutical Stabilization

• References: WO2005/020993, WO2005/020994, WO2008/0145143, WO2010/005980 (or WO2008/084698A1).
• Elements Taught: These references collectively teach sustained-release tacrolimus compositions, often in the form of solid dispersions, using hydrophilic or water-miscible vehicles like polyethylene glycol (PEG) and poloxamers, to improve bioavailability and achieve desired pharmacokinetic profiles. [cite: 1, 2, 3, US11419823B2 - Google Patents] WO '143 explicitly describes an extended-release oral dosage form of tacrolimus. WO '698 also describes a sustained-release tacrolimus solid dispersion.
• Motivation to Combine/Modify: A POSA would understand that while solid dispersions offer improved bioavailability for poorly soluble drugs like tacrolimus, they also increase the risk of chemical degradation compared to crystalline forms. [cite: US11419823B2 - Google Patents] The need for preventing degradation products in pharmaceutical formulations is a well-known concern, and strict regulatory restrictions exist regarding impurities. [cite: US11419823B2 - Google Patents] Therefore, it would be obvious for a POSA to seek ways to stabilize these known solid dispersion formulations of tacrolimus.
  • The patent itself states that "For tacrolimus-containing formulations, in particular formulations containing ingredients which may, as starting materials in the manufacturing process, contain traces of metals or metal compounds, oxidants and other undesirable but unavoidable contaminants, there is a need for preventing the formation of degradation products from tacrolimus or, at least, to maintain an acceptable, low concentration of such degradation products throughout the shelf-life of the formulation". [cite: US11419823B2 - Google Patents] This highlights an existing need known to a POSA.
  • The use of stabilizing agents, including pH-regulating excipients and chelating agents, to prevent drug degradation is a common pharmaceutical formulation strategy. A POSA would routinely explore such agents to address stability issues. The patent describes that tacrolimus degradation, specifically the formation of 8-epitacrolimus, occurs under mild basic and potentially mild acidic conditions. [cite: US11419823B2 - Google Patents] This would motivate a POSA to investigate pH adjustment as a stabilization strategy.
  • The concept of maintaining a specific pH to enhance stability is a fundamental principle in pharmaceutical chemistry. The patent specifically explores pH ranges below 7, noting that "the stabilizing agent is capable of providing a pH below 7 in the composition, as measured after re-dispersing the composition in water, more preferably a pH in the range of 2.5 to 5 or 2.5 to 4 or 3 to 3.6 or 3 to 3.5". [cite: US11419823B2 - Google Patents] This suggests an optimization within a known stabilization approach.

Combination 2: WO '993 / WO '994 / WO '143 / WO '980 (or WO '698) + Yamashita

• References: WO2005/020993, WO2005/020994, WO2008/0145143, WO2010/005980 (or WO2008/084698A1) and Yamashita (2003).
• Elements Taught: As above, the WO patents disclose tacrolimus solid dispersions in various vehicles for improved bioavailability and sustained release. Yamashita specifically teaches the preparation of solid dispersion formulations of tacrolimus, noting their stability at 40°C for 3 months. Yamashita explicitly states that "the supersaturated dissolution profiles of tacrolimus were observed in all SDFs, and the highest level of supersaturation for tacrolimus was obtained and maintained for 24h from SDF with HPMC. On the other hand, the supersaturated level from SDF with PEG 6000 or PVP decreased rapidly". It also clarified that "HPMC is the most appropriate carrier for SDF of tacrolimus".
• Motivation to Combine: A POSA would combine the knowledge from the WO patents regarding desired release profiles and solid dispersion technology with Yamashita's findings on the stability of tacrolimus solid dispersions. Yamashita identifies HPMC as a suitable carrier for stable tacrolimus solid dispersions. While Yamashita focuses on HPMC, it also discusses PEG 6000 and PVP, noting the rapid decrease in supersaturation from PEG 6000. The present patent, US 11,419,823, also lists HPMC as a useful hydrophilic or water-miscible vehicle and describes in Example 1B a Tacrolimus Composition B which includes HPMC and PEG 6000 and poloxamer 188. [cite: US11419823B2 - Google Patents] The fact that Yamashita investigated stability (3 months at 40°C) would naturally lead a POSA to consider further improving or maintaining stability in tacrolimus solid dispersions, particularly when formulating for sustained release. This would include exploring additional stabilizing agents like those claimed in US 11,419,823, such as organic acids or chelating agents, to address specific degradation pathways (e.g., 8-epitacrolimus formation) that might not be fully mitigated by the vehicle alone.

Combination 3: WO '993 / WO '994 + WO '109 + General Knowledge of Tacrolimus Instability and Stabilization

• References: WO2005/020993, WO2005/020994 and WO2007/091109A1.
• Elements Taught: WO '993 and WO '994 disclose solid dispersions of tacrolimus for improved bioavailability. WO '109 discusses tacrolimus in a stable amorphous form, while explicitly stating it is not a solid dispersion. However, WO '109 also references the poor water solubility of tacrolimus and its relatively low bioavailability, and it cites Honbo, T. et al. (1987) which discusses the oral dosage form of FK-506 (tacrolimus). It also mentions a tacrolimus containing composition in the form of solid dispersion, disclosed in EP 024773, containing lactose, hydroxypropyl methylcellulose, croscarmellose sodium and magnesium stearate as excipients.
• Motivation to Combine: A POSA would recognize that despite WO '109 distinguishing itself from solid dispersions, it still highlights the known issues of tacrolimus solubility and bioavailability, which solid dispersions (from WO '993 and WO '994) are designed to address. The mention of tacrolimus solid dispersion in EP 024773 in WO '109 further confirms that solid dispersions of tacrolimus were well-known prior art. The general understanding of tacrolimus's instability, as acknowledged in US 11,419,823, would motivate a POSA to combine the solid dispersion approaches of WO '993/WO '994 with common stabilization techniques, such as the addition of pH-regulating agents or chelating agents, to address degradation products like 8-epitacrolimus, which the present patent identifies as a major degradation product formed under mild conditions. [cite: US11419823B2 - Google Patents]

Motivation to Use Specific Stabilizing Agents (Organic Acids/Chelating Agents) and pH Control:

The patent explicitly states that the "present invention is based on the finding that a very important, i.e. major, degradation product of tacrolimus is the hitherto undisclosed C8-epimer of tacrolimus, also denoted 8-epitacrolimus". [cite: US11419823B2 - Google Patents] However, the degradation of pharmaceutical compounds and the use of stabilizing agents to prevent it are well-established practices.

• Metal Chelating Agents: The patent notes that "It has been found that formation of the major degradation product 8-epitacrolimus is decreased in the presence in the composition of a metal chelating agent." [cite: US11419823B2 - Google Patents] It explicitly identifies tartaric acid as having a chelating effect. [cite: US11419823B2 - Google Patents] The use of chelating agents to mitigate metal-catalyzed degradation is a common strategy in pharmaceutical formulation. A POSA, facing a degradation issue, would consider chelating agents if metal ion contamination was suspected or known to be a factor, especially given that "traces of e.g. metal ions will inevitably occur in the vehicle due to the use of equipment and excipients containing metal ions". [cite: US11419823B2 - Google Patents]
• Organic Acids (Citric, Tartaric, Oxalic): The patent highlights citric acid, tartaric acid, and oxalic acid as preferred stabilizing agents. [cite: US11419823B2 - Google Patents] These are commonly used pharmaceutical excipients known for their acidic and/or chelating properties.
  • Citric acid is a well-known acidulant and chelating agent in pharmaceutical and food industries.
  • Tartaric acid is also a known acidulant and chelating agent. The patent specifically demonstrates that tartaric acid and oxalic acid had an improved stabilizing effect compared to citric acid at 0.5% w/w. [cite: US11419823B2 - Google Patents]
  • Oxalic acid is also an acid and a chelating agent, though the patent notes it is "conventionally less useful in pharmaceutical compositions for regulatory reasons." [cite: US11419823B2 - Google Patents]
• pH Control: The patent emphasizes maintaining a pH below 7, preferably in the range of 2.5-5.0, more preferably 2.5-4.0, and even more preferably 3.0-3.6. [cite: US11419823B2 - Google Patents] Adjusting the pH of a formulation to optimize drug stability is a routine practice. The specific range would be determined through routine experimentation by a POSA to find the optimal balance for tacrolimus stability in the chosen vehicle system. The experiments in Example 7 of the patent, which demonstrate that "pH matters" and that "even a small pH increase has a significant effect on the stability of tacrolimus", would represent routine optimization for a POSA once the general strategy of pH control was identified. [cite: US11419823B2 - Google Patents]

Conclusion on Obviousness:

While US Patent 11,419,823 identifies 8-epitacrolimus as a "hitherto undisclosed" major degradation product and presents experimental data demonstrating the effectiveness of specific stabilizing agents and pH ranges, the core elements of the invention appear to be variations and optimizations of known pharmaceutical formulation principles. A POSA would have been motivated to combine existing knowledge of tacrolimus solid dispersions (from WO '993, WO '994, WO '143, WO '980, WO '698, and Yamashita) with general pharmaceutical stabilization strategies, including the use of pH-regulating agents and chelating agents, to address the known instability challenges of tacrolimus in solid dispersion systems. The selection of specific organic acids like citric, tartaric, or oxalic acid, and the optimization of their concentration and the resulting pH, would be considered routine experimentation within the skill of a POSA.

Therefore, the claims of US 11,419,823, particularly those related to the use of metal chelating agents or specific organic acids to achieve a stabilizing pH in a sustained-release tacrolimus solid dispersion, would likely be considered obvious to a person having ordinary skill in the art in light of the cited prior art and common pharmaceutical formulation knowledge.