Patent: 10,588,950

Summary for Patent: 10,588,950

Title:	Compositions and methods for counteracting Factor Xa inhibition
Abstract:	The disclosure provides compositions and methods for counteracting the effects of direct activated Factor X (FXa) inhibitors in a subject by administering a variant of FXa.
Inventor(s):	Pittman; Debra D. (Windham, NH), Camire; Rodney M. (Sicklerville, NJ), Fruebis; Joachim (Bedford, MA)
Assignee:	PFIZER INC. (New York, NY)
Application Number:	15/873,416
Patent Claims:	see list of patent claims

United States Patent 10,588,950: Critical Analysis of Claims and US Anticoagulant-Reversal Landscape

What does US 10,588,950 claim, in operational terms?

US Patent 10,588,950 is directed to methods for reversing anticoagulation caused by a direct Factor Xa (FXa) inhibitor (FXa inhibitors such as rivaroxaban and apixaban) in a subject with acute major bleeding and acquired coagulopathy. The reversal is effected by administering a Factor Xa variant engineered with amino-acid substitutions at two sequence positions relative to SEQ ID NO:1.

Core claim architecture (Claim 1 as the anchor)

Claim 1 requires all of the following:

1. Indication / clinical condition:
   • Subject has acute major bleeding and acquired coagulopathy due to FXa inhibition therapy using a direct FXa inhibitor.
2. Intervention:
   • Administer a Factor Xa variant containing at least one of two modification sets:
   • Position 235 (relative to SEQ ID NO:1) substituted with Thr, Leu, Phe, Asp, or Gly.
   • Position 236 (relative to SEQ ID NO:1) substituted with Leu, Ala, or Gly.
3. Functional performance constraint:
   • The variant must reverse the anticoagulant effect at a plasma concentration at least 250-fold lower than the plasma concentration of the direct FXa inhibitor.
4. Outcome:
   • Urgent reversal of the acquired coagulopathy due to FXa inhibition.

Claim set adds dose-response and timing

Claims 2-8 expand the method with quantitative efficacy and measurement parameters:

• Claim 2: bleeding reduction in a broad stepwise range (from 5%-10% through 95%-400%).
• Claim 3: thrombin production increase in stepwise magnitudes (from ≥10% up to 50-fold; includes 1.5-fold through 20-fold and 25-fold, 30-fold, 50-fold).
• Claim 4-5: clotting time reduction; PT as the assay.
• Claim 6: example PT targets (about 10-25 seconds in discrete steps).
• Claim 7: example INR targets (0.7-4.0 in discrete steps).
• Claim 8: PT measured at timepoints after administration of the FXa variant (from 15 min up to 90 min).

Claims define use cases and combinatorics

• Claim 9: administration schedule relative to surgery/injury/overdose.
• Claim 10: more than one administration.
• Claim 11-12: at least one additional procoagulant can be used; listed options include different FXa variant, Factor IX, Factor XIa, Factor XIIa, Factor VIII, Factor VIIa, FEIBA, and prothrombin complex concentrate (PCC).

Claims define inhibitor scope and pharmacologic ranges

• Claim 13: direct FXa inhibitor at supratherapeutic plasma concentration.
• Claim 14: inhibitor identity includes rivaroxaban, apixaban, betrixaban, darexaban, edoxaban, otamixaban.
• Claim 15: inhibitor plasma concentration ranges listed up to 800 nM (including 50, 100, 150, …, 800 nM).
• Claims 16-17: dosing and target plasma concentration ranges for the FXa variant (dose ranges in mg/kg; variant plasma concentration ranges from 0.0003 to 300 nM across multiple bands).
• Claims 18-20: narrower embodiment focusing on a single substitution at position 235 = Leu, and escalating potency requirements:
  • ≥250-fold (Claim 18),
  • ≥500-fold (Claim 19),
  • ≥1000-fold (Claim 20).

What is the “technical hook” that differentiates the patent?

The patent’s differentiator is not merely “FXa variant reversal,” but a specific combination of:

1. Two-position amino-acid engineering (positions 235 and 236 relative to a defined reference sequence), and
2. A quantified cross-concentration potency ratio requirement: reversal at ≥250-fold lower variant plasma concentration than the competing direct FXa inhibitor.

This creates a functional gating criterion that, from a claim-construction perspective, is harder to avoid than generic reversal strategies because it ties the engineered variant to a defined pharmacodynamic advantage against direct FXa inhibitors.

How strong is the claim scope versus generic reversal approaches?

Breadth in inhibitor identity and administration context

The claim set covers:

• Multiple direct FXa inhibitors (including major approved agents and less common/legacy pipeline molecules).
• Multiple clinical contexts: before surgery, after injury, after overdose.
• Multiple administration regimens (single or repeated dosing).
• Use with additional hemostatic agents (PCC/FEIBA and multiple clotting factors).

This broadens practical reach for enforcement across medical use.

Narrowness in the engineered molecule

The patent limits the active ingredient to Factor Xa variants with substitutions at positions 235 and/or 236 relative to SEQ ID NO:1. That narrow engineering definition can constrain design-around options, but also concentrates patentability risk if the prior art already teaches those same substitutions or teaches variants with equivalent potency.

Functional potency constraint can be a double-edged sword

The 250-fold plasma concentration ratio is protective if prior art variants do not reach that performance. But if earlier disclosures describe reversal efficacy without explicitly stating the same ratio, novelty/inventive step may still be attacked by:

• implicit disclosure theories,
• conversion of dose-response data to concentration ratios, or
• equivalence arguments, depending on the record.

In prosecution and litigation, this ratio likely becomes the battleground metric: whether the prior art or alternatives can be mapped onto “at least 250-fold” reversal at the same clinical endpoints.

Where are the legal vulnerabilities likely to concentrate?

Even without the full prosecution history, the claim text itself points to predictable challenges.

1) Position numbering dependence on SEQ ID NO:1

All substitutions are defined relative to SEQ ID NO:1. If that reference is not unambiguously linked to a canonical FXa sequence or if the reference sequence can be interpreted multiple ways, the scope could be litigated around what “position 235” and “position 236” truly mean in practice.

2) Functional result plus broad clinical condition language

Claim 1 ties efficacy to reversal of “acquired coagulopathy” and “urgent reversal,” with acute major bleeding as a clinical descriptor. “Urgent” is not defined quantitatively in claim text. While courts often handle timing terms with contextual interpretation, this can invite argument about whether the claim is sufficiently definite and whether prior art endpoints match the claimed “urgent reversal” standard.

3) Bleeding reduction and INR/PT range breadth (Claims 2 and 6-7)

Claims contain extremely broad stepwise ranges, including “95%-400%” for bleeding reduction (Claim 2). That breadth can cut both ways:

• It can support broad coverage if the patent’s experimental data includes such effects.
• It can also invite enablement or support challenges if the disclosed examples do not span those extremes.

4) Combination therapy breadth (Claims 11-12)

The claim permits additional procoagulants including PCC and FEIBA, plus multiple clotting factors and other FXa variants. Prior art combination approaches are common in hemostasis. If novelty is only in the FXa variant, then combination language may not distinguish well from earlier studies, and may increase obviousness vulnerability.

How does the patent likely sit in the US anticoagulant reversal landscape?

US 10,588,950 is part of the broader FXa reversal category that includes three main technical approaches:

1. Direct reversal agents (binding or neutralizing inhibitors; sometimes antibody fragments or small molecules)
2. Bypassing agents (PCC, FEIBA, recombinant factors, activated factors)
3. Engineered serine protease approaches (zymogen/protease variants that restore the coagulation cascade by counteracting inhibition)

This patent is squarely in engineered FXa variant territory, with an additional emphasis on concentration-based potency against direct FXa inhibitors.

Practical competitive framing (what matters for market and R&D)

For business strategy and investment decisions, two questions dominate:

• Can competitors engineer alternatives to the claimed position substitutions that still reverse at the same concentration ratio?
• Are there earlier disclosures (publications, WO filings, granted patents) that already describe:
  • FXa variants with substitutions at those positions, and
  • reversal effectiveness at comparable concentration ratios (or data that can be recomputed to show the same threshold)?

If the answer is yes to either, the claims may face validity pressure. If the answer is no, the potency ratio gives the patent a sharper fence.

Design-around map based on the claim constraints

A competitor looking to avoid literal infringement while still achieving reversal typically has three levers:

1. Change the engineered substitutions away from positions 235/236
   • Because Claim 1 is tied to substitutions at positions corresponding to 235 and 236 in SEQ ID NO:1, variants that do not alter these residues likely avoid literal coverage.
2. Keep the same substitutions but avoid the potency ratio requirement
   • If a variant reverses anticoagulation but does not demonstrate reversal at ≥250-fold lower plasma concentration, it may avoid the functional element.
   • However, this element may be hard to evade if potency is inherent to the mechanism and the data show equivalence.
3. Avoid “direct FXa inhibitor” scope or clinical state scope
   • Claim 1 requires acquired coagulopathy due to direct FXa inhibition therapy and acute major bleeding. Indications outside those conditions could avoid direct claim coverage, but regulatory strategy often targets exactly those emergency settings.

What to watch for in enforcement and claim construction

“At least 250-fold lower” as a measurable threshold

This is a clear numerical requirement. It will likely be treated as requiring comparison of:

• plasma concentration of the direct FXa inhibitor in the subject, and
• plasma concentration of the FXa variant, under conditions where reversal outcomes are measured (bleeding, thrombin, PT/INR).

Because both concentrations are dynamic, expert testimony around pharmacokinetics and sampling timepoints could matter.

PT/INR timepoints as secondary anchors

Claims 4-8 specify PT assay and measurement timings but do not require every timepoint. Still, the existence of defined windows can influence how courts interpret “urgent reversal” and relate clinical outcomes to laboratory endpoints.

Landscape implications for investors and R&D teams

If you are developing FXa variant reversers

• Patentability and freedom-to-operate hinge on whether your variant:
  • changes the same residues (235/236),
  • matches or exceeds the 250-fold threshold, and
  • produces reversal measured via PT/thrombin/bleeding endpoints.
• Your lead candidate should include concentration-ratio evidence designed to match how Claim 1 reads (not just generic hemostatic efficacy).

If you are developing alternatives to engineered FXa variants

• By-passing agents like PCC and FEIBA are already established; this patent’s novelty lies in engineered reversal with a quantitative potency ratio.
• Neutralizing binders may still face competitive pressure in emergencies because the engineered approach targets FXa activity downstream rather than neutralizing the inhibitor. But validity and enforcement will depend on whether the engineered approach is already known in the prior art with the same sequence positions and potency thresholds.

What’s missing from the provided record (and why it blocks a complete landscape answer)

A “comprehensive and critical analysis of the claims and the patent landscape” requires:

• the full text of US 10,588,950 (specification, definitions, dependent claim dependencies beyond the excerpt),
• claim chart logic tied to the granted claims,
• prosecution history, priority applications, and cited references, and
• competitor and prior-art patent mapping in the US (publications, grants, and litigated families) to evaluate novelty, obviousness, and enforceability.

With only the claim excerpt provided here, a full US landscape mapping cannot be performed without risking inaccuracies. The analysis above therefore focuses strictly on what is provable from the claim language: scope, distinguishing features, probable validity pressure points, and design-around logic.

Key Takeaways

• US 10,588,950 claims FXa variant-driven urgent reversal of direct FXa inhibitor-associated acute major bleeding, with efficacy gated by a ≥250-fold lower variant plasma concentration relative to the inhibitor.
• The engineered molecule scope is centered on residues corresponding to positions 235 and 236 in SEQ ID NO:1, with a narrower embodiment focusing on Leu at position 235 and potency thresholds up to ≥1000-fold.
• Dependent claims broaden coverage across PT/INR measurements, timing windows, dose and concentration ranges, clinical use cases, and combination co-therapies (PCC/FEIBA and multiple factors).
• The main enforceability battleground is likely the numerical concentration ratio and whether prior art can be mapped to the same engineered residue positions and concentration-based potency.
• Design-around efforts should avoid positions 235/236 and/or avoid meeting the ≥250-fold functional criterion.

FAQs

1. What is the single most important limitation in Claim 1?
   The Factor Xa variant must reverse the direct FXa inhibitor effect at a plasma concentration at least 250-fold lower than the inhibitor’s plasma concentration.

2. Which amino acids are specified for position 235?
   Thr, Leu, Phe, Asp, or Gly.

3. Which amino acids are specified for position 236?
   Leu, Ala, or Gly.

4. Does the patent limit the direct FXa inhibitor to one drug?
   No. It lists rivaroxaban, apixaban, betrixaban, darexaban, edoxaban, and otamixaban.

5. Can the method include other procoagulants?
   Yes. Claim 11-12 allows additional procoagulants including PCC, FEIBA, and multiple clotting factors.

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References

[1] U.S. Patent 10,588,950 (provided claim text).

Details for Patent 10,588,950

Applicant	Tradename	Biologic Ingredient	Dosage Form	BLA	Approval Date	Patent No.	Expiredate
Takeda Pharmaceuticals U.s.a., Inc.	AUTOPLEX, FEIBA NF, FEIBA VH	anti-inhibitor coagulant complex	For Injection	101447	December 21, 1979	10,588,950	2038-01-17
Takeda Pharmaceuticals U.s.a., Inc.	AUTOPLEX, FEIBA NF, FEIBA VH	anti-inhibitor coagulant complex	For Injection	101447	July 31, 2000	10,588,950	2038-01-17
Takeda Pharmaceuticals U.s.a., Inc.	AUTOPLEX, FEIBA NF, FEIBA VH	anti-inhibitor coagulant complex	For Injection	101447	August 11, 2005	10,588,950	2038-01-17