United States Patent 9,890,136: Claim Construction, Validity Risk, and Competitive Patent Landscape

What does US 9,890,136 claim, in technical and legal terms?

US 9,890,136 is a compound-and-use patent built around (i) a defined small-molecule scaffold with specific substitutions, and (ii) downstream therapeutic use tied to inhibition of histone deacetylases (HDACs), with particular emphasis on oncology.

Independent claim anchor

Claim 1 is the core. It recites:
- A “compound” of a specified structural class (a generic Markush-style framework), with variable substituents R1, R5, R6, Ar1 and constraints tying Ar1 to phenyl.
- R1 is defined as one of two linker/functional topologies:
  - R1 = --NR5--C(=O)--R6 or R1 = --C(=O)--NR5R6
- R5 and R6 are independently selected from hydroxyalkyl, aryl, heteroaryl, or C1-5 alkyl-aryl.
- Special restriction when Ar1 is phenyl:
  - R1 is “other than --C(=O)--NR5R6”, and within that restriction one of R5/R6 is phenyl or quinoline and the other is --CH2CH2OH.
- It also covers pharmaceutically acceptable salts.

This makes claim scope depend heavily on:

the scaffold (how R1 is positioned relative to the core),
the exact choice constraint “when Ar1 is phenyl,” and
whether the chemistry lands in the “other than” carve-out.

Dependent claim narrowing

The rest of the claim set tightens the variable space by:

specifying alternate Ar1 substitution patterns (Claims 2),
limiting R5/R6 to narrower sets (Claims 3, 4, 7, 15-17),
forcing more specific substituent identities via additional Markush fragments shown as structures in the patent text (Claims 5, 8, 15-18),
and adding method/composition claims (Claims 9-14, 19-22).

Non-compound coverage

Claim 9: pharmaceutical composition = compound of claim 1 + pharmaceutically acceptable carrier.
Claims 10-12: method of inhibiting HDAC activity in cells; Claim 11 specifies HDAC6.
Claims 12-14: treating cancer in a subject; Claim 13 adds periodic dosing plus an anti-cancer agent.
Claims 19-22 repeat composition and cancer treatment framework for the narrower compounds of dependent compound claims (notably claim 18).

How broad are these claims in practice?

Scope drivers

The broadest practical axis is the Markush language:

R5 and R6: hydroxyalkyl, aryl, heteroaryl, and C1-5 alkyl-aryl.
R1 topology: allows both amide-like carbonyl arrangements involving NR5 and R6.

However, breadth is curtailed by a conditional structure constraint:

Ar1 is phenyl and then R1 must be “other than --C(=O)--NR5R6”, while requiring:
- one of R5/R6 is phenyl or quinoline, and
- the other is --CH2CH2OH.

This is a high-leverage limitation that can substantially shrink coverage if the marketed or competing compound has a different Ar1 substitution or uses the disallowed R1 topology.

HDAC6 linkage

The “inhibiting HDAC6” language appears only in Claim 11. That matters because:

A competitor using HDAC inhibition without targeting HDAC6 might still fall under broader HDAC inhibition language in Claim 10, but not the HDAC6-specific limitation in Claim 11.
Litigation typically treats dependent claims as narrower. The independent inventive proposition is HDAC inhibition generally (Claim 10), while HDAC6 is a secondary narrowing.

Combination therapy claims

Claims 13 and 21 require periodic administration of:

the claimed compound (or salt), plus
an anti-cancer agent selected from a very long list.

Two points for landscape impact:

The long list reads like an “open-ended” combination claim framed as “selected from [many agents],” which reduces arguments that a given combo is outside the enumerated set if the competitor uses a common oncology standard.
The list also includes known HDAC inhibitor comparators (e.g., SAHA/vorinostat, tretinoin ATRA, and others). That can broaden the combination claim coverage and also increases the chance the examiner applied obviousness rationales if combination therapy was already known.

What are the main validity risks for US 9,890,136?

A critical analysis on validity must separate:

(A) chemical-genus novelty/obviousness exposure, from
(B) method-of-use patentability exposure under obviousness-type reasoning, and
(C) claim-definiteness and enablement risk for Markush breadth.

A. Chemical-genus obviousness pressure

This patent’s genus is built on:

an HDAC-inhibitor-like heteroatom-rich architecture, with
substituent diversity through Markush variables R5/R6.

Such scaffolds are typically viewed by examiners and courts as:

chemically predictable,
optimization-friendly (substituent swapping to tune potency/selectivity, solubility, and PK),
and therefore vulnerable to obviousness if close prior art exists that already discloses:
- the same core scaffold,
- the same carbonyl-amine arrangement (R1),
- and similar terminal groups (e.g., hydroxyalkyl and aryl/heteroaryl N-substitutions).

The conditional restriction tied to R5/R6 = phenyl or quinoline + --CH2CH2OH looks like an “optimization embodiment” that could be argued as an obvious selection within a known set, if prior art disclosed multiple candidates and one of them had that exact combination.

B. Method-of-use obviousness pressure

The claims include:

HDAC inhibition in cells (Claim 10),
cancer treatment (Claim 12),
and combination therapy with specified classes of oncology drugs (Claims 13, 21).

In most HDAC inhibitor landscapes, cancer indications and general anti-cancer utility often face strong obviousness attacks because:

HDAC enzymes are established cancer targets,
prior HDAC inhibitors were known to induce anti-proliferative effects,
and combination regimens with standard-of-care agents are commonly disclosed.

Thus, even if the compound itself has novelty, the incremental utility language may not add patentable weight unless the specification and claim scope capture a distinct and nonobvious biological property tied to the chemical structures.

C. Enablement/definiteness risk for Markush-like breadth

The Markush variables create an expansive chemical space:

hydroxyalkyl, heteroaryl, aryl, and C1-5 alkyl-aryl for both R5 and R6.

Potential risk areas in this kind of genus claim:

if the disclosure does not teach how to make and test the full breadth with reasonable effort, or
if the biological data supports only a subset, leaving large portions of the claim unsupported by enablement.

The claim language also uses conditional structure constraints (“when Ar1 is phenyl…”). Courts analyze whether these constraints are clear and whether the genus is properly bounded.

Where the claims are likely to land in the prior-art space

The claimed design:

includes a carbonyl and amine linkage (R1),
includes hydroxyalkyl functionality (--CH2CH2OH),
and includes aromatic/heteroaromatic groups (phenyl, quinoline).

That combination is characteristic of HDAC inhibitor families that often incorporate:

a zinc-binding/coordination motif (or functional equivalent),
a cap group (aryl or heteroaryl),
and a linker with hydrogen-bonding features.

Even without the full chemical drawing shown in the provided excerpt, the functional substituent set signals that the claimed compounds likely sit near known “cap group + linker + hydroxyl” HDAC designs. That proximity typically drives obviousness risk for a broad Markush genus.

How strong are the claims commercially (enforceability and “design-around”)?

Enforcement leverage

Claim 1 is broad at the formula level, and it includes pharmaceutically acceptable salts.
The combination therapy claims (Claims 13 and 21) can create leverage where competitors must differentiate dosing regimens and co-administered agents.

Design-around levers

Competitors can attempt to step outside the claim set by changing at least one of these:

the Ar1 definition so that the conditional “when Ar1 is phenyl” constraint does not apply,
the R1 topology, specifically landing the compound in the excluded topology when Ar1 is phenyl,
both R5 and R6 substitution identities so that the key pairing “phenyl or quinoline + --CH2CH2OH” is not met where required, and
the HDAC biology: avoiding HDAC6-specific claims if only Claim 11 is asserted (while still potentially risking Claim 10 if broader inhibition is shown).

Combination claims are harder to design around if the competitor uses a standard-of-care agent on the enumerated list. But competitors can restructure regimens to avoid the “periodic administering” structure or avoid co-administration with the listed agent categories, depending on how “periodically” and “anti-cancer agent” are construed during enforcement.

Patent landscape implications: what matters for competitors

1) Compound-focused vs. method-focused battles

In an HDAC inhibitor space, litigations often hinge on:

whether the accused compound matches the Markush ranges tightly enough, and
whether method claims can be proven by use evidence.

Here:

the most enforceable hook is Claim 1 (direct compound coverage),
then Claim 10/12/20 (use),
and last Claim 13/21 (combination, periodic regimen, plus listed anti-cancer agents).

If a competitor’s compound avoids Claim 1, the downstream method/composition claims typically collapse because they are built directly on “the compound of claim 1” or “the compound of claim 18” type dependencies.

2) The HDAC6 specification

Claim 11’s HDAC6 limitation is significant for portfolio mapping:

If a competitor’s compound is primarily an HDAC1/2 inhibitor rather than HDAC6 selective, they have a cleaner route to avoid Claim 11.
But the independent method claim (Claim 10) still captures general HDAC inhibition, so the biological distinction needs to be strong and consistent across assays.

3) Combination regimen breadth

Claims 13 and 21 list a very large set of oncology agents. That tends to:

reduce the “not listed” defense,
increase the chance that any mainstream oncology combination falls within the claim,
push the design-around strategy toward regimen structure (timing and periodicity) and co-administration practice rather than selection of a non-listed anti-cancer agent.

Competitive intelligence: claim-value map by asset type

Asset type	Claim numbers	Scope character	Practical strength
Core chemistry	1, 6, 7, 15-18	Wide Markush genus with conditional constraints	Highest leverage if competitor overlaps R5/R6 and R1 topology
Narrowed chemistry	2-5, 8, 14, 16-18	More restrictive substituent definitions	Useful for fallback coverage in litigation
Composition	9, 19	Requires compound + carrier	Moderate; usually derivative of compound claim validity
Cellular HDAC inhibition	10-11	Functional biological claim; includes HDAC6 specificity in 11	Moderate; depends on proving inhibition in cells
Cancer treatment	12, 20	Indication-based method claim	Moderate; depends on how obvious utility is over known HDAC oncology
Combination therapy	13, 21	periodic administration + specified anti-cancer agents	Medium to high if accused regimen matches structure and timing

What is missing for landscape completeness in this record

The provided excerpt contains claim text but does not include:

the patent’s specification details,
the prior art cited during prosecution,
the prosecution history,
or the publication number of the application family.

Without that, a precise “whole-landscape” mapping cannot be produced here in a defensible way (for example, which exact prior art references disclose the same scaffold, or whether claim 1 is patentably distinct from earlier HDAC inhibitor series). The analysis above therefore focuses on the claim architecture and predictable validity/enforceability dynamics for this kind of HDAC inhibitor patent.

Key Takeaways

Claim 1 is the central enforceable right and is a broad Markush genus constrained by conditional “when Ar1 is phenyl” restrictions that specifically govern R1 topology and require a specific pairing involving phenyl or quinoline and --CH2CH2OH.
Method claims (HDAC inhibition and cancer treatment) are derivative and likely face obviousness pressure common to HDAC oncology utility, while HDAC6 specificity is only explicitly present in Claim 11.
Combination claims are broad on agent selection due to a long enumerated list, shifting design-around efforts toward regimen structure and co-administration timing rather than changing the partner drug.
The overall portfolio value depends on whether the disclosed genus is supported across the full Markush range (enablement) and whether prior art already disclosed close analogs with predictable substituent swaps (obviousness).

FAQs

Is HDAC6 required to infringe?
Not for all method coverage. Claim 10 covers “histone deactylase,” while Claim 11 narrows to HDAC6 specifically.
What is the biggest structural constraint in Claim 1?
The conditional restriction tied to Ar1 being phenyl, which constrains R1 (“other than --C(=O)--NR5R6”) and requires one of R5/R6 = phenyl or quinoline and the other = --CH2CH2OH.
Do composition claims broaden the compound scope?
No. Claims 9 and 19 depend on the covered compound(s); they generally do not expand chemical scope beyond the compound claims.
How can competitors design around combination claims?
By avoiding a match to the claim structure for “periodically administering” the compound together with a listed anti-cancer agent, and by adjusting co-administration practices where feasible.
Where is enforceability likely strongest: compound or method?
Typically compound claims (Claim 1 and its dependent chemistry claims) provide the strongest enforcement basis; method claims often turn on proving biological effect and can face broader obviousness attacks.

References

[1] United States Patent 9,890,136. “Claims” section as provided in the user prompt.

Applicant	Tradename	Biologic Ingredient	Dosage Form	BLA	Approval Date	Patent No.	Expiredate
Recordati Rare Diseases, Inc.	ELSPAR	asparaginase	For Injection	101063	January 10, 1978	9,890,136	2034-12-23
Merck Sharp & Dohme Llc	INTRON A	interferon alfa-2b	For Injection	103132	June 04, 1986	9,890,136	2034-12-23
Merck Sharp & Dohme Llc	INTRON A	interferon alfa-2b	For Injection	103132		9,890,136	2034-12-23
>Applicant	>Tradename	>Biologic Ingredient	>Dosage Form	>BLA	>Approval Date	>Patent No.	>Expiredate

Patent: 9,890,136

Summary for Patent: 9,890,136