From Off-Label Use to Approved Indication: How Rare Disease Treatments Evolve Through Indication Expansion

By:DengYue International Business Division

Introduction

In rare disease treatment, some of the most important therapies did not begin as formally approved treatments for those conditions.

Instead, they often started as medications used in other diseases, later showing unexpected benefits in rare patient populations.

Over time, through clinical research, real-world evidence, and regulatory review, many of these therapies progress from off-label use to officially approved indications through a process known as indication expansion.

Understanding this pathway is essential for recognizing how medical innovation actually reaches rare disease patients.

From Clinical Observation to New Treatment Possibility

Drug development is not always a linear process.

In many cases, new therapeutic uses are first identified in real-world clinical practice rather than in initial drug development plans.

This may happen when:

● Physicians observe unexpected treatment responses

● Early research reveals shared biological mechanisms

● Small patient groups respond positively to existing drugs

● Academic studies explore alternative disease pathways

These early signals often form the foundation for further investigation.

What Is Indication Expansion?

Indication expansion refers to the formal process by which a previously approved drug receives regulatory approval for a new disease or condition.

Unlike off-label use, which occurs in clinical practice, indication expansion is a regulated approval pathway that requires:

● Additional clinical trials

● Safety and efficacy evaluation in the new indication

● Submission of regulatory documentation

● Review by health authorities

Once approved, the new indication becomes part of the official prescribing label.

Why Rare Diseases Often Rely on Existing Drugs

Rare diseases present unique challenges for drug development.

Small patient populations

Limited patient numbers make traditional large-scale trials difficult.

High development cost

Developing a completely new drug for a very small population is often economically challenging.

Unmet medical needs

Many rare diseases still have limited or no approved treatments available.

As a result, existing drugs with known safety profiles are often evaluated for potential use in rare disease settings.

Key Pathways That Lead to New Indications

1. Shared biological mechanisms

Many rare diseases share common molecular pathways with more common conditions.

This allows drugs targeting specific proteins or genes to be tested across multiple diseases.

2. Real-world clinical experience

In some cases, consistent positive outcomes in clinical practice encourage further formal research.

These observations can lead to structured clinical studies.

3. Investigator-initiated studies

Academic researchers and hospitals often conduct early exploratory trials to evaluate new uses for existing drugs.

These studies frequently serve as the first step toward formal approval.

Examples of Successful Indication Expansion

1)    Imatinib

Originally developed for chronic myeloid leukemia, imatinib later demonstrated significant benefits in gastrointestinal stromal tumors (GIST), including rare tumor subtypes.

Its expansion into multiple indications marked a major milestone in targeted cancer therapy.

2)    Rituximab

Initially approved for lymphoma and rheumatoid arthritis, rituximab has since been widely studied in:

● Neuromyelitis optica spectrum disorder (NMOSD)

● Autoimmune encephalitis

● Immune-mediated kidney diseases

Many of these uses began as off-label treatments before becoming supported by clinical guidelines and further regulatory review.

3)    Eculizumab

Originally approved for paroxysmal nocturnal hemoglobinuria (PNH), eculizumab later expanded into additional rare complement-mediated disorders, including atypical hemolytic uremic syndrome (aHUS).

What Indication Expansion Means for Rare Disease Patients

Indication expansion plays a critical role in improving access to treatment.

Faster access to innovation

Patients may benefit from therapies years before new drug development programs are completed.

Expanded therapeutic options

Existing drugs can be applied across multiple rare disease categories.

Stronger evidence over time

As data accumulates, treatment decisions become increasingly evidence-based.

Challenges in the Expansion Process

Despite its importance, indication expansion faces several barriers:

Lengthy regulatory timelines

Even when strong evidence exists, formal approval can take years.

Limited commercial incentives

For older or off-patent drugs, manufacturers may have reduced motivation to pursue new indications.

Regional differences

Approval status may vary significantly between countries and regulatory systems.

The Role of Global Healthcare Access

Because regulatory approvals and indication expansion timelines vary across countries, rare disease patients often face significant differences in treatment availability worldwide.

A therapy may already be:

●  approved in one region

●  still under review in another

●  or supported only by clinical evidence without formal indication expansion

This creates a fragmented global treatment landscape, where access to innovation depends not only on science, but also on geography and regulatory timing.

In this context, navigating treatment options often requires understanding not just medical evidence, but also how drugs move through different regulatory systems.

DengYue operates in this intersection between clinical evidence and global drug accessibility, helping to map how innovative therapies, including those involved in indication expansion processes, are evolving across different healthcare systems.

Rather than focusing on a single market, this perspective allows patients and healthcare stakeholders to better understand:

●  where a therapy is already available

●  where it is still emerging

●  and how global development pathways may influence future access

Conclusion

The journey from off-label use to approved indication reflects how medical innovation actually progresses in rare disease treatment.

Many transformative therapies begin with early clinical observation, evolve through real-world use, and eventually become formally approved treatments through indication expansion.

For rare disease patients, this pathway represents an important bridge between existing medicines and new therapeutic possibilities.

As precision medicine continues to advance, indication expansion will remain a key mechanism driving the development and global availability of innovative treatments.