A friend of mine works in a preclinical lab. His company runs the kind of studies that are supposed to tell the FDA whether a drug is safe enough to test in humans. Over the past couple of years each round has been taking longer because the number of parameters keeps going up, which is a polite way of saying regulatory requirements have been accumulating faster than anyone's ability to keep track of them.
They hired a consultant. The consultant was supposed to make sure the IND package (the Investigational New Drug application you file with FDA before you can dose your first patient) included everything it needed. Some of the required studies still didn't get done. They had to go back, repeat work, re-validate. In an industry where reproducibility is its own KPI, "we had to redo the study" is not a scheduling inconvenience. It is an existential problem.
I'm a software person. I got into this the way I get into most things: a friend with a regulatory background pointed me at the problem, and I started reading. ICH M3(R2) first (the master guideline for what nonclinical safety studies you need before human trials), then S7A and S7B for safety pharmacology, then S2(R1) for genotoxicity testing, then the actual Code of Federal Regulations, Title 21 Part 312, which is the legal text governing IND applications and which reads like it was written to be deliberately incomprehensible.
They're all like that, by the way. Long, dense, cross-referencing each other. I doubt anyone reads any of them start to finish voluntarily. The people who know these documents best are the regulatory lawyers who bill by the hour to interpret them for you.
At some point I found a 90-page NIH manual from 2019 about IND submissions that I'm fairly sure has been downloaded fewer times than it has pages.
After all that reading I went looking for a checklist. A simple IND readiness checklist with what you need, sorted by Common Technical Document module, with links to the rules that require it. It does not exist. FDA guidance runs hundreds of pages. Consulting firm blogs give you four paragraphs of advice so vague it could apply to any regulated industry and then a contact form. So I made one.
Download the full checklist: FDA IND Submission Checklist (PDF) — 50 items organized by CTD module, linked to ICH/FDA sources. Free, no email.
What FDA reviewers actually care about
When a reviewer picks up your IND, the questions are not complicated. Can this drug be safely given to a human, based on the animal data you've submitted. Can you manufacture it the same way twice. Is your clinical trial designed to produce useful data without injuring the participants.
Nonclinical safety package, CMC, protocol.
If the package doesn't clearly answer all three you get a clinical hold per 21 CFR 312.42. FDA tells you to stop, fix the gaps, and resubmit. For a company spending half a million dollars a month on runway that is not an abstraction. It is the scenario that comes up in every conversation I have with regulatory affairs people, and I've had more of those conversations than I expected since January.
The IT architecture analogy. The rules don't change that often. The checks aren't even that complicated if you know where to look. This is an IT architecture problem, fundamentally. If you think about your system architecture at the end of development, after you've already built everything, it's going to be bad. Same dynamic here. Plan your IND-enabling study architecture before you start running studies, or discover the compliance gaps when it's expensive to fix them.
The problem isn't that the requirements are secret or impossible. The problem is that there are a lot of documents, each one is long, and there are nuances you only learn about by going through the IND submission process. At which point you've already spent the money.
Take the pre-IND meeting
Before I get into the actual IND submission requirements — if you're a first-time sponsor, request a Type B pre-IND meeting with FDA. Technically optional. Practically essential.
You submit a briefing document with your nonclinical program design, proposed clinical protocol, and CMC strategy. FDA responds in writing. The meeting itself is 60 minutes. What you get back is the closest thing to a cheat sheet that exists in this process: specific feedback on whether your IND-enabling studies are sufficient, whether your starting dose justification makes sense, and whether your CMC package needs work.
Teams that skip the pre-IND meeting to "save time" reliably spend more time dealing with clinical hold letters. The FDA meeting request process is straightforward. File the request, wait 60 days, have the meeting. Details at regfo.com/library/m1-admin/meetings.
Paperwork: Module 1
Form FDA 1571 is the main IND application form. Filling it out for the first time is roughly the experience of doing your taxes if your taxes were longer and the penalty for a mistake was the FDA telling you to go away.
You also need the Form FDA 1572 (Statement of Investigator — one per clinical site), the Form FDA 3674 (ClinicalTrials.gov certification), a cover letter, a table of contents, an introductory statement, and a general investigational plan. Environmental assessment or categorical exclusion claim. Financial disclosures for each investigator. Debarment certification.
None of this is intellectually difficult. All of it is tedious in the way that only government forms can be, and nobody tells you about any of it until you're trying to file and googling "FDA Form 3674 fillable PDF" at midnight.
One thing that catches first-time filers: the entire submission must be in eCTD format. Electronic Common Technical Document. Specific file naming, PDF bookmarks, module placement. It's not optional in 2026 and the formatting alone can delay your filing by weeks if you haven't planned for it.
The full Module 1 breakdown is at regfo.com/library/m1-admin.
Nonclinical studies: the IND-enabling package
Most clinical holds originate here. Module 4 of the CTD.
Toxicology
You need repeat-dose toxicity studies conducted in two species under Good Laboratory Practice (GLP per 21 CFR Part 58): one rodent, one non-rodent. Duration must equal or exceed your planned clinical dosing period — ICH M3(R2) Table 1 has the exact mapping. Single-dose toxicity can sometimes be addressed within the repeat-dose study design rather than as a standalone study, but you need to justify that.
The missing non-rodent species is the gap I hear about most often, and it's not close. Teams run their rat studies, get good results, start assembling the IND, and somewhere around month three somebody actually reads ICH M3(R2) and discovers they also need dog or primate data. Beagle studies do not schedule themselves. CRO slots for large-animal tox are booked months out.
This is essentially what happened at my friend's lab. The consultant was supposed to catch it. Consultants do help, I should say. I'm not dismissing the entire profession. But as in any industry, a consultant is partly an insurance policy, and how much that policy is worth depends entirely on how much you trust the specific person. In this case, the studies that should have been flagged weren't, and the work had to be repeated. In preclinical research, repeating a study means re-establishing reproducibility, re-validating batches, re-spending money you already spent. It compounds.
Safety pharmacology and the hERG trap
Safety pharmacology covers cardiovascular function (including a cardiac ion channel assay called hERG per ICH S7B), central nervous system effects, and respiratory function. All studies must be conducted under GLP. This is the core battery required by ICH S7A.
The hERG trap. A company runs a non-GLP hERG assay early in development, for internal decision-making. Reasonable. They get a clean result. Then they file the IND with that same non-GLP data because "the result is the same either way, GLP is just more paperwork." GLP is not just more paperwork. GLP is the thing that makes FDA accept your data. Non-GLP hERG = clinical hold, every time. The assay costs ~$30-40K. Companies delay their entire program by months to avoid that. I have stopped trying to understand the logic.
Genotoxicity standard battery
Genotoxicity testing per ICH S2(R1) requires a standard battery. Two options:
- Option 1: Ames test (bacterial reverse mutation) + mammalian cell chromosomal assay + in vivo micronucleus test
- Option 2: Ames test + in vivo micronucleus + in vivo Comet assay
Both options include an in vivo component as part of the standard battery — it's not just a follow-up for positive in vitro results. This catches people.
Pharmacokinetics
PK/ADME data — absorption, distribution, metabolism, excretion in two species. Basic characterization is sufficient for Phase 1. You also need plasma protein binding data (it feeds into the starting dose calculation). And don't forget bioanalytical method validation.
Reproductive toxicology
If your Phase 1 trial enrolls only men, ICH M3(R2) lets you skip reproductive toxicity studies entirely. The moment you include women of childbearing potential, you need embryo-fetal development studies in two species (typically rat and rabbit — matters for CRO selection and timeline). The trap is the mid-study decision. Enrollment is slow, someone suggests broadening the eligible population, and now you need studies that weren't budgeted, weren't scheduled, and will add months to the timeline. I know of a rare disease program where exactly this happened. Added five months and roughly $400,000 in unplanned costs. The investigator wasn't angry at FDA. He was angry at his own team for not asking "what if we expand enrollment?" during planning and working out what that would cost.
The batch comparability trap
There's a related problem that isn't obvious until you see it happen. Your toxicology batch and your clinical batch need to be comparable. The material you tested in animals and the material you plan to give humans. That's technically a CMC question, but it surfaces as a nonclinical problem when your non-rodent study is delayed and you've changed your manufacturing process in the interim. Now you're trying to argue that different batches are equivalent while simultaneously waiting for toxicology data you don't have.
CMC: Chemistry, Manufacturing, Controls
Module 3 of the CTD. Not my area — I've been deep in tox and pharmacology, not drug formulation, and I'd rather say that than get the details wrong.
FDA requires drug substance specifications, a manufacturing process description, an impurity profile (including genotoxic impurities per ICH M7), a drug product formulation, and certificates of analysis. Container closure system description. Batch analysis for at least 1-2 batches of clinical material.
Good news for Phase 1: full cGMP is not required, but appropriate manufacturing controls must be documented. Full analytical validation isn't needed either — phase-appropriate data is sufficient. The FDA Phase 1 CMC guidance spells this out.
Requirements are at regfo.com/library/m3-quality.
Clinical protocol: the starting dose math
Your protocol includes the expected elements: objectives, endpoints, patient selection criteria, dose escalation scheme with DLT definitions and stopping rules, safety monitoring, IRB approval, informed consent. None of that is where the tension is.
The tension is in the dosing rationale. Reviewers want to see the NOAEL (no-observed-adverse-effect level) from your animal studies, the drug exposure at that level, your proposed human equivalent dose, and the safety margin between them. How wide that safety margin needs to be is — remarkably — not specified in the FDA starting dose guidance, which creates exactly the confusion you'd predict. The FDA's 2005 guidance on estimating safe starting doses codifies a default 10-fold safety factor below the HED derived from the NOAEL. This is not negotiable for a standard first-in-human study.
One team told me they'd submitted with a 3-fold margin on a non-cancer drug. "Our compound is well-tolerated," they said, as if that meant the math didn't apply. FDA sent questions.
Cancer drugs under ICH S9 have more flexibility on starting dose and toxicology requirements, but I tried to summarize oncology IND rules once and got corrected on three points, so I'm leaving that for a separate post.
You also need an Investigator's Brochure per ICH E6(R2). The IB is where first-time filers struggle more than they expect. It's a compiled reference document that every investigator at every site receives, and it needs to include: a summary of your drug's physical and chemical properties, a summary of all nonclinical pharmacology and toxicology findings, a summary of PK data, and — critically — a clear description of known and potential risks. Reviewers use the IB to judge whether your investigators will have enough information to protect their patients. A thin IB signals a thin program.
Top 10 clinical hold triggers
These are the gaps that actually stop IND applications, based on 21 CFR 312.42 and what I've heard from regulatory professionals:
- Missing non-rodent tox species. CRO large-animal slots book months out — plan early.
- Non-GLP hERG assay submitted as pivotal. Costs ~$30-40K to do right. Non-GLP = automatic hold.
- Tox study duration shorter than planned clinical dosing. ICH M3(R2) Table 1. Match the durations.
- Insufficient starting dose justification. Show the NOAEL → HED → safety margin math. ≥10x for non-cancer.
- CMC batch inconsistency. Provide batch analysis. Demonstrate comparability if process changed.
- Incomplete genotoxicity battery. Standard battery includes an in vivo component. Both options.
- Protocol doesn't address known animal findings. Monitoring plan must cover every target organ from tox.
- Informed consent missing known risks. ICF must list every adverse finding from nonclinical studies.
- Inadequate exposure margins in tox species. Animal wasn't adequately exposed relative to proposed human dose — distinct from starting dose math.
- Tox batch ≠ clinical batch. Plan manufacturing so tox and clinical material use the same process.
After you file
FDA has 30 calendar days to review your IND per 21 CFR 312.40. The IND becomes effective on Day 30 unless a clinical hold is issued. During those 30 days your IRB can review the protocol, sites can prepare, but you cannot dose anyone.
Once active: expedited safety reports per 312.32, annual reports per 312.33, protocol amendments per 312.30. The IND is a living document.
Where things break
Recovery groups are a judgment call. That's where you include a group of animals that stops receiving the drug partway through the study, so you can demonstrate that toxic effects are reversible. A toxicologist I've worked with recommends them by default on any repeat-dose study longer than 14 days. She argues that adding recovery groups costs about $50,000, while a six-week delay from FDA asking reversibility questions costs multiples of that. I think she's right when you have organ findings. On a clean study, I've heard of people filing without recovery groups and getting no questions, so the honest answer is that it depends.
I don't love that answer. But it's the accurate one.
What this doesn't cover
Cancer drugs, biological products, gene therapies, cell therapies — each operates under a different regulatory framework and compressing any of them into a paragraph would do more harm than good. Pediatric development plans are not required at the initial IND stage. The CTD Library at regfo.com/library has 218 sections covering all of these for anyone who wants to go deeper.
The checklist
I compiled everything above — plus the CMC details, the Module 2 summaries, and the items I deliberately left out of the narrative because they're boring but necessary — into a single PDF organized by CTD module. Every item is marked Required, Conditional, or N/A for Phase 1. Every item links to the ICH guideline or CFR section that requires it, plus the corresponding page in our CTD Library.
Download the FDA IND Submission Checklist (PDF) — free, no email required.
What to do with this
This is a list of what goes in the box. Whether your studies actually satisfy these IND submission requirements is a harder question, and in my experience it's the one that teams confront about three weeks before their planned filing date, which is not a great time to discover that you're missing a study.
If a friend asked me what Regfo does — no marketing, just over a beer — I'd say it tells you upfront which studies you need so you only run the ones that actually move you toward FDA approval. Instead of hiring someone expensive to read guidelines on your behalf, you upload your reports, check them against 24 guidelines and 1,054 rules, and know where you stand in about three minutes. The other approach involves two weeks and a spreadsheet that becomes less useful the bigger it gets.
Related: ICH Q1 Revision: Everything That's Changing in Stability Testing
FAQ
What documents are required for a Phase 1 IND submission?
A Phase 1 IND requires documents across five CTD modules. Module 1 (Administrative): Form FDA 1571, Form FDA 1572 for each clinical site, Form FDA 3674, cover letter, table of contents, introductory statement, general investigational plan, financial disclosures, debarment certification, and an environmental assessment or categorical exclusion claim. Module 2: nonclinical and clinical overviews and summaries. Module 3 (CMC): drug substance and drug product specifications, manufacturing process description, impurity profile per ICH Q3A/Q3B, certificates of analysis, and container closure description. Module 4 (Nonclinical): GLP repeat-dose toxicity in two species, safety pharmacology per ICH S7A/S7B, genotoxicity per ICH S2(R1), and PK/ADME data. Module 5 (Clinical): investigational protocol, Investigator's Brochure per ICH E6(R2), and informed consent form. The full list of 50 items organized by module is in the IND checklist PDF.
How long does FDA take to review an IND?
FDA has 30 calendar days to review an IND after receipt, per 21 CFR 312.40. If FDA doesn't contact you by Day 30, the IND becomes effective automatically — you can begin dosing patients on Day 31 (assuming IRB approval is in hand). If FDA issues a clinical hold, they must notify you in writing within those 30 days and schedule a follow-up call within 30 days of issuing the hold. There's no expedited lane for IND review — the 30-day clock applies regardless of disease area or urgency unless FDA chooses to act earlier. During those 30 days your team can prepare clinical sites and finalize IRB review, but no patient dosing.
What is the 30-day safety review period?
The 30-day safety review period is the window FDA has under 21 CFR 312.40 to evaluate your IND after submission. The clock starts when FDA receives your complete package. If FDA finds the safety data sufficient, the IND goes into effect on Day 30 without formal notification — silence means assent. If FDA identifies safety gaps under 21 CFR 312.42, they issue a clinical hold letter before Day 30. This mechanic means sponsors spend those 30 days in an anxious wait with no interim feedback. FDA doesn't provide progress updates during the window. One common confusion: the 30-day period is calendar days, not business days. Submitting on a Friday doesn't extend your runway.
Can I submit an IND without a pre-IND meeting with FDA?
Yes, the pre-IND meeting is optional under FDA regulations — there's no requirement in 21 CFR 312 to hold one before submitting. But skipping it reliably costs more time than it saves. A Type B pre-IND meeting gives you FDA's written feedback on your nonclinical program adequacy, proposed clinical protocol, and CMC strategy before you commit to a filing date. The meeting request process takes about 60 days: submit a briefing document, wait for FDA's written response, then hold the 60-minute meeting. If FDA flags a study gap in that process, you fix it before spending the money to assemble the IND. Teams that skip the pre-IND meeting to "move faster" frequently encounter clinical holds that delay first dosing by 6-12 months.
What happens if my IND is incomplete?
If your IND is missing required elements or contains safety data FDA deems inadequate, FDA will issue a clinical hold letter under 21 CFR 312.42. The letter specifies the gap. You then have unlimited time to address it — there's no hard deadline on the sponsor side — but the clock is running on your burn rate. After you submit a complete response addressing each point in the hold letter, FDA has 30 days to review it and either lift the hold or issue another response. If the gap is a missing toxicology study, add 5-9 months for CRO scheduling and study execution. If it's a documentation issue (buried dose justification, missing GLP statement), you might resolve it in 6-8 weeks. The total cost of a clinical hold at a company burning $400K/month averages $2.4M in runway for a 6-month delay.
Do I need GLP studies for a Phase 1 IND?
Yes. All pivotal nonclinical safety studies in your IND — repeat-dose toxicity, safety pharmacology core battery, and genotoxicity standard battery — must be conducted under Good Laboratory Practice per 21 CFR Part 58. Non-GLP data can be included as supporting or exploratory context, but it can't serve as the basis for safety conclusions or starting dose calculations. The most common GLP mistake is submitting a non-GLP hERG assay as pivotal cardiovascular safety data. FDA rejects it every time. A GLP-compliant hERG costs $30-50K. A non-GLP hERG costs less, but causes a clinical hold that runs 3-6 months minimum. Phase-appropriate relief exists for CMC (full analytical validation isn't required at Phase 1), but there's no phase-appropriate relief for the GLP status of pivotal safety studies.
What's the difference between an original IND and an IND amendment?
An original IND is your first submission under 21 CFR 312.23 — it establishes a new IND number and covers an initial clinical investigation. Once the IND is active, all subsequent changes go through IND amendments per 21 CFR 312.30-312.31. Protocol amendments cover new protocols, changes to existing protocols, or new investigators. Information amendments cover updates to nonclinical data, CMC information, or other technical content that doesn't require a separate amendment type. Annual reports per 21 CFR 312.33 summarize all IND activity for the prior year and are due within 60 days of the IND's anniversary date. Safety reports per 21 CFR 312.32 must be submitted within 7 calendar days (IND safety reports for unexpected fatal or life-threatening serious adverse events) or 15 calendar days (all other unexpected serious adverse events). The IND number persists through all amendments and phases.