Understanding Clinical Trials

Preclinical

Identify drug candidates, test safety and efficacy in cell cultures and animal models, develop manufacturing processes

Phase 1

Evaluate safety, determine safe dosage range, identify side effects, study how the drug is absorbed and metabolized

Phase 2

Evaluate effectiveness, further assess safety, determine optimal dosage and delivery method

Phase 3

Confirm effectiveness in large diverse populations, monitor side effects, compare to existing treatments, gather data for labeling

FDA Review

FDA reviews all trial data, manufacturing processes, and labeling. Advisory committees may convene. Priority Review available for serious conditions.

Phase 4

Monitor long-term safety, detect rare side effects, study use in special populations, and optimize treatment protocols

Government Grants (NIH/NEI)

The National Institutes of Health (NIH) and its National Eye Institute (NEI) fund early-stage research and some clinical trials through grants (R01, U01, R21). NIH invests ~$45 billion annually in biomedical research. Academic investigators often use NIH grants for Phase 1/2 trials.

Pharmaceutical & Biotech Industry

Large pharma companies and biotech firms fund the majority of late-stage clinical trials. They invest in programs with commercial potential, often acquiring promising therapies from smaller companies after early positive results.

Venture Capital & Private Equity

VC firms fund early-stage biotech startups developing novel therapies. They provide capital for preclinical work and early clinical trials in exchange for equity. Gene therapy companies are particularly attractive to VC due to high potential returns.

Nonprofit Foundations & Patient Advocacy

Disease-specific foundations fund research directly, support clinical trial infrastructure, and provide patient assistance. For rare diseases like IRDs, foundations often fill funding gaps that industry overlooks due to small patient populations.

Crowdfunding & Patient Communities

Patients and families increasingly fund research through crowdfunding platforms and community fundraising. While individual amounts are smaller, collective efforts can seed early research or fund specific trial sites.

Understanding Clinical Trials

Learn how clinical trials work for inherited retinal diseases. Understand phases, eligibility, risks, and how to enroll.

A comprehensive guide to how new treatments are developed, tested, and approved — from laboratory discovery through FDA approval and beyond. Specifically relevant to inherited retinal disease (IRD) therapies including gene therapy, RNA therapy, and cell-based treatments.

How Clinical Trials Work

A clinical trial is a carefully designed research study conducted in human volunteers to answer specific questions about the safety and effectiveness of a new treatment, drug, device, or medical procedure. Clinical trials are the gold standard for determining whether a new therapy works and is safe enough for widespread use.

Purpose

Clinical trials determine whether a new treatment is safe and effective. They measure outcomes like vision improvement, disease stabilization, or slowed progression — comparing results against a placebo or existing standard of care.

Participants

Participants volunteer after meeting specific eligibility criteria (age, diagnosis, genetic mutation, disease stage). For IRD trials, genetic testing confirmation is typically required. Participants receive the experimental treatment and are closely monitored.

Informed Consent

Before enrolling, participants receive a detailed explanation of the study's purpose, procedures, risks, benefits, and alternatives. Consent is voluntary and can be withdrawn at any time. An Institutional Review Board (IRB) must approve all consent documents.

Oversight & Safety

Every trial is overseen by an IRB (ethics committee), a Data Safety Monitoring Board (DSMB), and the FDA. These bodies can pause or stop a trial if safety concerns arise. Regular safety reports are submitted throughout the study.

Key Trial Design Concepts

Preclinical Research

Before any therapy can be tested in humans, years of preclinical work must establish that it is reasonably safe and has a scientific basis for effectiveness. For gene therapies targeting IRDs, this process is particularly rigorous due to the complexity of delivering genetic material to retinal cells.

1. Target Identification & Validation

Researchers identify the specific gene mutation causing the disease and validate that correcting or compensating for it can restore function. For IRDs, this involves studying the gene's role in retinal cell biology and confirming that the protein product is essential for photoreceptor or RPE cell survival.

2. Drug/Vector Development

For gene therapy: selecting the appropriate viral vector (typically AAV serotypes like AAV2, AAV5, AAV8, or AAV9 for retinal delivery), designing the transgene cassette with appropriate promoters, and optimizing the construct for efficient transduction of target cells. For small molecules: medicinal chemistry optimization of lead compounds.

3. In Vitro Studies (Cell Culture)

Testing in cell lines and patient-derived iPSC retinal organoids to confirm the therapy reaches target cells, expresses the correct protein, and doesn't cause toxicity. These studies provide initial proof-of-concept before moving to animal models.

4. Animal Model Studies

Testing in animal models of the disease (mice, rats, dogs, or non-human primates with equivalent genetic mutations). For IRDs, naturally occurring animal models exist for many conditions (e.g., RPE65-deficient Briard dogs were crucial for Luxturna development). Studies assess biodistribution, efficacy (ERG, OCT, behavioral vision tests), and toxicology.

5. GMP Manufacturing & Toxicology

Developing Good Manufacturing Practice (GMP) processes to produce clinical-grade material. For gene therapy vectors, this includes scaling up production, ensuring purity and potency, and establishing quality control assays. Formal toxicology studies in relevant species (often non-human primates for ocular therapies) are required before filing an IND.

The Different Phases of Clinical Trials

Clinical trials progress through distinct phases, each with specific objectives, participant numbers, and success criteria. A therapy must successfully complete each phase before advancing to the next. The entire process from Phase 1 to approval typically takes 6–12 years.

IRD-Specific Considerations

For inherited retinal diseases, clinical trials often combine Phase 1 and Phase 2 (Phase 1/2 dose-escalation studies) because the patient populations are small and the diseases are rare. Many IRD gene therapy trials enroll fewer than 50 patients total. The FDA's Orphan Drug Designation, Breakthrough Therapy Designation, and Accelerated Approval pathways can significantly shorten timelines for rare disease therapies. Luxturna (voretigene neparvovec), the first FDA-approved gene therapy for an IRD, took approximately 20 years from initial research to approval (1996–2017), but newer programs are progressing faster with improved vector technology and regulatory experience.

Application & Approval Process

The regulatory pathway from laboratory to patient involves multiple applications, reviews, and approvals. In the United States, the FDA oversees this process. Gene therapies and biologics follow a slightly different path than traditional drugs.

Investigational New Drug (IND) Application

Before starting any clinical trial in humans, the sponsor must file an IND application with the FDA. This comprehensive document includes all preclinical data, manufacturing information, the clinical protocol, and investigator qualifications.

• Animal pharmacology and toxicology data

• Manufacturing and quality control information

• Clinical protocols and investigator information

• Previous human experience (if any)

• FDA has 30 days to review after submission

• If no "clinical hold," trial may proceed

• Annual reports required throughout trial

• Safety reports due within 15 days of serious events

Institutional Review Board (IRB) Approval

Every clinical trial site must receive approval from an IRB — an independent committee of physicians, scientists, and community members who ensure the study is ethical, that risks are minimized, and that informed consent is adequate. The IRB reviews the protocol, consent forms, and recruitment materials. They conduct ongoing monitoring throughout the trial and can suspend studies if participant safety is compromised.

New Drug Application (NDA) or Biologics License Application (BLA)

After successful Phase 3 trials, the sponsor submits an NDA (for drugs) or BLA (for biologics like gene therapies) to the FDA requesting marketing approval. This is a massive submission — often exceeding 100,000 pages — containing all preclinical and clinical data.

Advisory Committee & Decision

The FDA may convene an advisory committee of external experts to review the data and vote on whether the benefits outweigh the risks. While advisory committee votes are not binding, the FDA follows their recommendation in most cases. For Luxturna, the advisory committee voted unanimously (16-0) in favor of approval. Once approved, the therapy can be marketed and prescribed, though the FDA may require post-marketing studies (Phase 4) or a Risk Evaluation and Mitigation Strategy (REMS).

Special FDA Designations for Rare Diseases

For diseases affecting fewer than 200,000 people in the US. Provides 7 years of market exclusivity, tax credits for clinical trials, and waived FDA filing fees. Most IRD therapies qualify.

For therapies showing substantial improvement over existing treatments. Provides intensive FDA guidance, rolling review, and organizational commitment. Luxturna received this designation.

Specifically for cell therapies, gene therapies, and tissue-engineered products. Provides all benefits of Breakthrough Therapy plus eligibility for accelerated approval and priority review.

For therapies addressing serious conditions with unmet medical need. Enables rolling review (FDA reviews sections as they're completed rather than waiting for the full submission) and more frequent FDA meetings.

How Long Clinical Trials Take

The journey from initial discovery to an approved therapy is long and uncertain. On average, it takes 10–15 years and only about 10% of drugs that enter clinical trials ultimately receive FDA approval. For gene therapies targeting rare diseases, timelines can be shorter due to expedited regulatory pathways, but the science remains complex.

Stage

Typical Duration

Key Activities

Basic Research

2–5 years

Gene identification, disease mechanism studies, target validation

Preclinical Development

3–6 years

Vector design, animal studies, toxicology, GMP manufacturing

IND Filing + Phase 1

1–2 years

Safety assessment, dose escalation, initial efficacy signals

2–3 years

Efficacy confirmation, dose optimization, expanded safety

2–4 years

Large-scale efficacy, comparative studies, registration-enabling

6–18 months

BLA/NDA review, advisory committee, PDUFA date

Total (Discovery → Approval)

10–15 years

Can be 6–8 years with expedited pathways for rare diseases

Why IRD Trials Can Move Faster

Cost of Clinical Trials

Developing a new therapy is extraordinarily expensive. A 2024 JAMA study found the median cost of bringing a drug from discovery to market is approximately $350 million for rare diseases, though costs can exceed $2 billion when accounting for the cost of failed programs. Gene therapies tend toward the higher end due to complex manufacturing requirements.

Phase

Cost Range

Key Cost Drivers

Why Gene Therapy Costs More

• Manufacturing complexity: GMP-grade AAV vector production requires specialized facilities and extensive quality testing

• Surgical delivery: Subretinal injection requires vitreoretinal surgeons and operating room time

• Long-term follow-up: Gene therapy requires years of monitoring for durability and delayed effects

• Small batches: Rare disease populations mean smaller manufacturing runs at higher per-unit cost

Cost-Reducing Factors for IRDs

• Smaller trial sizes: Rare disease trials may need only 30–100 patients vs. thousands for common diseases

• Orphan Drug incentives: Tax credits cover 25% of clinical trial costs

• Academic partnerships: University-based trials leverage existing infrastructure

• Platform technologies: Same AAV vector platform can be adapted for multiple IRD targets

How Clinical Trials Get Funded

Funding a clinical trial requires substantial capital from multiple sources. The funding landscape for IRD therapies is unique because rare disease economics often require creative partnerships between government, industry, nonprofits, and patient communities.

Typical Funding Journey for an IRD Gene Therapy

Explore Active IRD Clinical Trials

See which therapies are currently in development for inherited retinal diseases, from early Phase 1 studies through FDA-approved treatments.

Active Clinical Trials

Browse all active clinical trials for inherited retinal diseases.

Treatment Pipeline

Track gene therapies and treatments progressing through clinical development.

Find a Specialist

Connect with research centers conducting IRD clinical trials.