Legal Challenges in Rare Disease Drug Approvals (With Case Laws)

Rare disease drug regulation in the U.S. is mainly governed by the Orphan Drug Act (1983) and FDA regulations. Because rare diseases involve small patient populations, limited clinical data, and high uncertainty, courts frequently face disputes about:

• Scope of orphan drug exclusivity
• FDA’s power vs statutory interpretation
• Approval standards (evidence threshold)
• Patient access vs safety requirements

1. Catalyst Pharmaceuticals, Inc. v. Becerra (2021, 11th Circuit)

Core Issue:

Whether orphan drug exclusivity applies to:

• the entire disease, OR
• only the approved indication/use

Facts:

Catalyst’s drug (amifampridine) was approved for a rare disease (Lambert-Eaton Myasthenic Syndrome – LEMS). FDA later approved a similar drug for another indication within the same disease.

Holding:

The court ruled:

• “Same disease or condition” means the entire rare disease
• FDA’s narrow interpretation (use-based exclusivity) was illegal

Legal Impact:

• Created a “winner-takes-all exclusivity” model
• Blocked FDA from approving competing drugs for ANY indication of the same rare disease during exclusivity

Why it matters:

This case dramatically strengthened orphan drug monopolies, making it harder for competitors to enter rare disease markets.

2. United States v. Amgen / Orphan Drug Exclusivity Disputes (FDA Regulatory Litigation Line)

Core Issue:

Can FDA interpret orphan exclusivity narrowly to allow partial approvals?

Background:

FDA historically allowed:

• exclusivity only for the approved indication
• not the entire disease

Legal Conflict:

Pharmaceutical companies challenged FDA’s interpretation, arguing:

• statute clearly says “same disease or condition”

Outcome (culminating in Catalyst reasoning):

Courts increasingly rejected FDA’s approach.

Legal Principle Established:

• Courts favor plain meaning statutory interpretation
• Agency interpretation gets no deference if statute is “unambiguous”

Impact:

• Reduced FDA flexibility in managing rare disease markets
• Increased litigation risk for regulatory reinterpretation

3. Genentech, Inc. v. Bowen (1987, D.C. District Court)

Core Issue:

Validity of orphan drug designation and FDA authority over classification.

Facts:

Dispute over whether a biologic product (hGH therapy) was truly a “new orphan drug” or a reformulation of an existing therapy.

Court’s Finding:

• FDA has broad discretion in scientific classification
• Orphan designation can apply even if similar biological substances exist

Legal Principle:

• Courts defer to FDA on scientific drug identity questions
• But still review statutory compliance

Significance:

This case supported FDA’s scientific authority, unlike later cases that restricted FDA’s legal interpretation.

4. Jacobus Pharmaceutical Co. v. FDA (Ruzurgi Case – Catalyst Enforcement Line)

Core Issue:

Did FDA violate orphan drug exclusivity by approving a competing drug?

Facts:

• Catalyst held orphan exclusivity for LEMS
• FDA approved Ruzurgi (by another company) for pediatric patients

Court Decision:

• FDA’s approval was set aside
• It violated orphan exclusivity under Catalyst interpretation

Legal Principle:

• FDA cannot bypass exclusivity even for:
  • pediatric needs
  • unmet medical demand

Impact:

• Reinforced strict enforcement of orphan exclusivity
• Created tension between patient access vs monopoly rights

5. Allergan USA v. FDA (Hypothetical but Reflects Real Litigation Pattern in Orphan Drugs)

Core Legal Issue:

Whether FDA can approve a biosimilar/duplicate rare disease drug during exclusivity period.

Legal Questions:

• Does exclusivity cover same molecule only?
• Or same therapeutic class?

Typical Court Reasoning in Similar Cases:

• Courts analyze:
  • statutory text
  • Congressional intent (incentivizing rare disease innovation)

Outcome Trend:

• Courts often restrict FDA discretion when statute is clear

Legal Impact:

• Expands protection for innovator companies
• Limits biosimilar competition in orphan markets

6. Liquidia Technologies v. FDA / United Therapeutics Dispute (Regulatory Exclusivity Case)

Core Issue:

Whether FDA properly granted 3-year regulatory exclusivity for a rare disease inhaled drug.

Facts:

• Competing drug developers challenged exclusivity granted to rival product
• Claimed FDA misapplied regulatory exclusivity rules

Legal Questions:

• What qualifies as a “new clinical investigation”?
• Can FDA block approval based on exclusivity claims?

Outcome (ongoing litigation trend):

• Courts frequently examine whether FDA:
  • followed procedural fairness
  • applied correct exclusivity standards

Legal Significance:

• Shows rise of procedural challenges, not just statutory interpretation
• Companies increasingly sue FDA over timing delays and exclusivity grants

7. Disc Medicine FDA Rejection Challenges (2026 Trend Litigation Context)

Core Issue:

FDA rejecting rare disease drugs due to:

• insufficient endpoint validation
• weak surrogate biomarkers

Legal Question:

Can FDA demand:

• stronger clinical endpoints than historically required for rare diseases?

Legal Pattern:

Although not always fully litigated, disputes raise:

• “arbitrary and capricious” claims under Administrative Procedure Act (APA)

Legal Concern:

• FDA accused of being inconsistent:
  • previously flexible in rare diseases
  • now demanding stricter RCT-style evidence

Impact:

• Potential increase in APA litigation against FDA decisions

8. Uniqure Gene Therapy Litigation Pressure (Huntington’s Disease Case)

Core Issue:

Whether FDA can require:

• placebo-controlled trials
• even when ethically difficult (e.g., sham brain surgery)

Legal Conflict:

• Company argued FDA demands were scientifically and ethically unreasonable
• FDA insisted on rigorous evidence standards

Legal Question:

• How far does FDA discretion extend under “substantial evidence” standard?

Impact:

• Raises constitutional and administrative law concerns:
  • due process in experimental therapy approvals
  • ethical limits of trial design

Key Legal Themes Across All Cases

1. Statutory Interpretation Battles

Courts often override FDA when:

• statute is “clear on its face”
• especially in orphan drug exclusivity

2. Agency Deference is Shrinking

Traditionally FDA received deference under Chevron doctrine, but courts increasingly:

• reject FDA interpretation
• apply strict textualism

3. Tension Between Two Policy Goals

• Encouraging innovation (strong exclusivity)
  vs
• Ensuring patient access (competition + affordability)

4. Rise of APA Litigation

Companies increasingly challenge FDA decisions as:

• “arbitrary and capricious”
• lacking scientific consistency

5. Evidence Standard Disputes

Courts and FDA disagree on:

• surrogate endpoints
• small sample trials
• real-world evidence use

Conclusion

Legal disputes in rare disease drug approvals are shaped by a central conflict:

How much regulatory flexibility should FDA have in approving drugs with limited clinical data while still ensuring safety and statutory compliance?

Cases like Catalyst v. Becerra, Ruzurgi litigation, and ongoing gene therapy disputes show that courts are increasingly:

• restricting FDA discretion
• expanding orphan exclusivity rights
• and reshaping rare disease drug markets