Understanding Bridging Trials in India for Foreign Drug Approvals

Introduction

India, one of the largest pharmaceutical markets globally, plays a critical role in both the consumption and manufacturing of drugs. As multinational companies look to introduce their approved drugs into the Indian market, a key regulatory requirement often arises: the need for bridging studies. These studies help confirm the relevance of global clinical trial data to the Indian population, especially when no prior Indian data exists or when ethnic, genetic, or environmental factors may influence drug response.

The Central Drugs Standard Control Organization (CDSCO), through its New Drugs and Clinical Trials Rules (NDCTR), 2019, lays down specific conditions under which bridging studies are required, exempted, or substituted. Sponsors planning market access in India must understand the regulatory framework, scientific rationale, and operational logistics involved in planning these studies. This article provides a comprehensive overview of bridging study requirements in India, including guidance from global agencies like ICH (E5), CDSCO’s expectations, waiver possibilities, and submission strategies.

Background / Regulatory Framework

What Are Bridging Studies?

Bridging studies are additional clinical trials conducted in a new region or country to confirm the extrapolation of foreign clinical data to a local population. These studies may include pharmacokinetic (PK), pharmacodynamic (PD), efficacy, safety, or dose-finding elements, depending on regulatory expectations.

ICH E5 Guidance and Its Relevance in India

The concept of bridging studies originates from ICH E5: “Ethnic Factors in the Acceptability of Foreign Clinical Data.” ICH E5 classifies ethnic factors as intrinsic (genetic, age, weight, organ function) and extrinsic (medical practice, diet, compliance) — all of which may impact drug response.

India, while not a formal ICH member until recent years, aligns many of its regulatory practices with ICH guidelines. CDSCO often refers to ICH E5 while deciding on the necessity of bridging studies.

NDCTR 2019 and CDSCO Position on Bridging Trials

Under NDCTR, foreign clinical data can be submitted for marketing approval. However, Rule 75 of NDCTR empowers CDSCO to mandate additional Indian clinical data (i.e., a bridging study) when:

• The drug has not been marketed in any country
• The Indian population may respond differently
• There is insufficient data from Indian subjects
• The disease burden or treatment patterns are unique in India

CDSCO’s Subject Expert Committees (SECs) play a decisive role in evaluating the need for a bridging trial.

Core Clinical Trial Insights

1. Types of Bridging Studies in India

Bridging studies in India may take the form of:

• Pharmacokinetic Studies: To compare drug absorption, distribution, metabolism, and elimination in Indian vs. foreign populations
• Bioequivalence Studies: For generics or modified dosage forms
• Phase III Trials: When efficacy or safety in Indian patients needs confirmation
• Hybrid Trials: Combining global and Indian arms

CDSCO prefers local PK or PD studies where ethnic variability is suspected.

2. When Bridging Studies Are Mandatory

Bridging studies are typically required when:

• The foreign trial has no Indian subjects
• The drug’s therapeutic index is narrow
• The pharmacogenomic profile of Indian patients differs
• The condition has unique epidemiology in India (e.g., TB, malaria)

CDSCO is especially cautious with oncology, cardiology, and CNS drugs due to variability in response and safety signals.

3. CDSCO Waiver of Bridging Studies

Bridging trial requirements may be waived if:

• The drug is approved in major ICH countries (US, EU, Japan)
• The company submits a robust justification referencing ICH E5
• Post-marketing surveillance data is strong
• The disease burden is high and unmet medical need exists

In such cases, CDSCO may approve based on a “clinical trial waiver” issued by the SEC. However, post-approval commitments such as PMS or Phase IV trials may still apply.

4. Application Process for Bridging Study

To conduct a bridging study in India, applicants must:

• Submit a CT-04 application form to CDSCO via SUGAM portal
• Provide Investigators’ Brochure, Protocol, IMPD, and prior data
• Include rationale for local study (or justification for waiver)
• Register the trial with the Clinical Trials Registry–India (CTRI)

All trials must be conducted in accordance with GCP, ICMR guidelines, and approved by an Ethics Committee registered with CDSCO.

5. Sample Size and Site Selection

Sample size for a bridging study depends on the variability of endpoints and the statistical power required. For PK bridging studies, 24–48 healthy volunteers may suffice. For efficacy confirmation trials, 100–300 patients may be enrolled.

Sites must be GCP-compliant and have the necessary infrastructure for safety monitoring, data handling, and cold-chain logistics (if applicable).

6. Common Challenges in Bridging Studies

Challenges include:

• Recruiting patients within tight timelines
• Aligning global and local data formats
• Ethics Committee delays
• Differing regulatory expectations between CDSCO and FDA/EMA

Sponsors often partner with CROs experienced in bridging studies to mitigate operational and compliance risks.

7. Case Examples

Example 1: A cardiovascular drug approved in Japan underwent a 60-subject Indian PK study due to CYP enzyme metabolism differences. CDSCO waived the need for an efficacy trial based on Japanese data and Indian PK results.

Example 2: A novel anti-diabetic agent approved in the US was required to undergo a 200-patient bridging Phase III study in India due to differing dietary patterns and background therapies. Approval followed after successful bridging data.

Best Practices & Preventive Measures

• Align bridging strategy early in global development
• Include Indian sites or subjects in pivotal global trials
• Prepare ICH E5-compliant justification documents
• Consult CDSCO via pre-submission meetings
• Monitor ethnic variability and extrapolation limits from published studies

Scientific & Regulatory Evidence

• ICH E5: Ethnic Factors in the Acceptability of Foreign Clinical Data
• NDCTR 2019: Rule 75, Schedule Y
• CDSCO GCP Guidelines: Section 2.3 on multi-regional studies
• WHO TRS 850, 1995: Acceptability of foreign clinical data
• ICMR Ethical Guidelines: Considerations for Indian populations

Special Considerations

Ethnic Variability in India

India’s population is genetically diverse, with significant variations in drug-metabolizing enzymes (e.g., CYP2C9, CYP2C19). This supports the rationale for local PK/PD studies for certain classes of drugs, such as anti-epileptics or anticoagulants.

Pediatric and Geriatric Bridging

Bridging studies in children and elderly require special design. CDSCO mandates child-specific trials unless global pediatric data includes Indian subjects or a waiver is granted with sufficient justification.

Decentralized Trials and Digital Consent

For bridging studies during the COVID-19 period, CDSCO allowed remote consent and home-based data collection. These methods must be backed by validated SOPs and Ethics Committee approval.

When Sponsors Should Plan Bridging Studies

• Early in Phase III global planning to avoid duplication
• When India is a major launch market for the molecule
• If previous Indian trials were inconclusive or delayed
• When therapeutic class has known ethnic differences
• When post-approval surveillance is inadequate

FAQs

1. What is the difference between a bridging study and a global trial?

A bridging study is conducted to support data transferability from a foreign population to Indian subjects. A global trial is conducted concurrently across countries including India.

2. Can bridging trials be waived entirely?

Yes, if the drug is approved in major countries and shows no expected variability, CDSCO may waive the requirement based on ICH E5 justifications.

3. How long does CDSCO take to approve a bridging trial?

It typically takes 3–4 months from submission to final approval, depending on SEC meeting schedules and completeness of the application.

4. Are bridging studies applicable to medical devices?

Yes. For high-risk medical devices or when human factor validation is necessary, CDSCO may request local clinical investigation even if global data exists.

5. Can bioequivalence (BE) studies act as bridging studies?

In some generic drug approvals, a BE study in Indian subjects is accepted as a bridging study, especially if the reference product was not approved in India previously.

Conclusion

Bridging studies in India serve a critical function in ensuring that foreign clinical data is relevant, safe, and effective for Indian patients. Sponsors should adopt a proactive strategy, understand CDSCO expectations, align their global and Indian regulatory plans, and where possible, integrate Indian cohorts into global trials. Bridging studies, though sometimes seen as additional burdens, can significantly strengthen local market access and post-approval confidence.