eIND: exploratory IND versus emergency IND

eIND may be referred to as either exploratory Investigational New Drug (IND) or emergency Investigational New Drug (IND). An "Exploratory IND" and an "Emergency IND" are both regulatory mechanisms used in the United States by the Food and Drug Administration (FDA) to allow for the use of investigational drugs in certain circumstances. It's important to note that the exploratory IND and emergency IND represent distinct concepts.

Exploratory IND (eIND):

exploratory IND may be called 'Phase 0' clinical trial. Exploratory IND was described in FDA Guidance for Industry, Investigators, and Reviewers "Exploratory IND Studies". The guidance defined the exploratory IND as the following:

Purpose: Used for early-stage clinical trials to explore the preliminary pharmacokinetics and the pharmacodynamics features, not the safety and efficacy of a new drug or treatment. The dose is sub-therapeutic level or micro-dose.

Timing: Typically used in the early stages of drug development, before a drug has been extensively studied in humans and before the phase 1 study

Process: Requires submission of an IND application to the FDA, detailing the proposed clinical trial protocol, preclinical data, and any available safety information. However, less pre-clinical data or animal data is required for the eIND study than for the typical phase 1 study.

Review: The FDA reviews the eIND application and provides feedback before the trial can proceed.

Requirements: Investigators must adhere strictly to the protocol outlined in the IND application, and any deviations must be reported to the FDA.

Emergency IND (eIND):

Emergency Use Investigational New Drug (IND) applications are part of expanded access program (also referred to as compassionate use). expanded access program was described in 21 CRF Part 312 "Subpart I—Expanded Access to Investigational Drugs for Treatment Use". FDA has a designated page to describe the "Expanded Access" process. 

emergency INDs may also be called single-patient INDs, Individual Patient Expanded Access, or Single Patient Expanded Access. They are initiated in urgent scenarios where immediate access to an unapproved drug is necessary, and the clinical circumstances do not permit the time required for a standard IND submission. emergency INDs are primarily utilized in cases of life-threatening conditions where no established treatment options are available.

21 CRF Part 312.310 described the process for expanded access for individual patients, including for emergency use. 

Purpose: Used in emergency situations where there is no alternative treatment available, and the patient's condition is serious or life-threatening.

Timing: Typically used when there is an urgent need to provide access to an investigational drug outside of a clinical trial setting.

Conditions: Reserved for cases where standard treatments have failed, are unavailable, or are not suitable for the patient.

Review: The FDA still needs to review the emergency IND application, but needs to provide feedback / approval in a very short period (hours/days).