What "Investigational" Means

A word that does a lot of heavy lifting

What investigational means is a question that rarely gets answered where the word appears most. It turns up in abstracts, in ethics approvals and in press releases announcing the next big thing, and the accompanying commentary almost never stops to explain it. Which, I'd argue, is a fairly significant omission.

Because "investigational" is not a synonym for "promising" or "almost proven" or "the science is there, we're just waiting on paperwork." It has a specific meaning. Understanding that meaning is one of the most useful pieces of research literacy you can develop if you spend any time reading about cannabinoids, peptides, or phytomedicines.

The word is also slippery because it is accurate in so many different situations. It can describe something with a single small safety study behind it, and it can describe something that has run the full gauntlet of trials and is waiting on a regulator's decision. A reader who sees the label and nothing else cannot tell which of those they are looking at.

What investigational means in a regulatory sense

In the context of drug development and regulatory affairs, "investigational" describes a substance or intervention that is under formal scientific study but has not yet been approved for general therapeutic use by a medicines regulator. In Australia, that regulator is the Therapeutic Goods Administration (TGA). In the United States it's the FDA; in Europe, the EMA. Our explainer on the Therapeutic Goods Administration sets out how the Australian body works.

The TGA's framework is worth understanding specifically. A substance listed on the Australian Register of Therapeutic Goods (see our ARTG glossary entry for the full picture) has cleared a defined evidence threshold for safety and efficacy in a specific indication. An investigational substance has not. It may be under active study. It may have cleared early-phase safety trials. It may have decades of preclinical data behind it. But it has not completed the regulatory pathway that ends in approved use for general prescribing. For a longer look at the register itself, see the ARTG and the difference between registered and unregistered medicines.

Notice the phrase "in a specific indication." Approval is not a general stamp of quality on a compound. It is a decision about one use, in one population, supported by one body of evidence. That is why a substance can be approved for one purpose and still be investigational for another.

Why the label gets misread

This distinction matters because the word is often used in ways that blur the line. "Investigational" sounds like a bureaucratic technicality, a hoop the substance is about to jump through. Sometimes it is. Often it isn't. A great many investigational compounds never make it to approval. The attrition rate in clinical drug development is sobering: estimates across therapeutic areas generally put the probability of a Phase I compound reaching market approval at somewhere between 10% and 14%, depending on the disease category and how you count withdrawn applications. Most investigational things stay investigational, or get shelved entirely.

Those figures come with caveats of their own. Success rates vary by disease area, by the type of compound and by how a study counts compounds that are paused rather than formally abandoned. The sensible reading is not a precise odds calculation but a sense of scale: the default outcome for an investigational compound is not approval.

How investigational status sits inside the clinical trial framework

Clinical research is staged. This isn't arbitrary. The stages exist because you genuinely can't know what you don't know until you look carefully, in humans, at escalating scales. If you want the longer version of that story, how clinical trials move from lab to patient walks through it, and the general outline is also covered in this Wikipedia overview of the phases of clinical research.

Phase I trials are primarily about safety and dosing. They're typically small; sometimes fewer than 30 participants, and they don't tell you whether the compound does what you hope it does in a clinical sense. Phase II trials start examining efficacy signals and continue building the safety picture. Phase III trials are the large, often randomised, controlled studies that form the backbone of a regulatory submission. Phase IV happens post-approval and tracks real-world performance over time.

A compound can be described as "investigational" at any point before regulatory approval. That means a substance with only Phase I data is investigational. A substance that just failed a Phase III trial is also investigational. The word covers an enormous range of evidence quality, and reading it as a signal of near-certain efficacy is a mistake I see made constantly, including by science journalists who genuinely know better.

Why does the staging matter so much? Small early studies are good at spotting obvious safety problems but poor at detecting rarer effects or at separating a real signal from chance. Larger, controlled designs exist to reduce those weaknesses. Our piece on how psychedelic clinical trials are designed shows how design choices such as blinding and comparison groups shape what a trial can honestly conclude.

Special access pathways are not the same as approval

Australia has mechanisms that allow patients to access unapproved therapeutic goods under specific circumstances, notably the Special Access Scheme (SAS) and the Authorised Prescriber framework. Our Special Access Scheme entry covers the mechanics in detail, and the Authorised Prescriber page explains how that pathway works for individual clinicians. For a broader view, understanding the Special Access Scheme in Australia is a good companion read.

What these pathways do not do is transform an investigational substance into an approved one. They create a legal channel for access under defined conditions. The substance remains unapproved. The clinician takes on additional accountability. The patient typically provides informed consent that acknowledges the investigational nature of what they're receiving. These are important, considered mechanisms; but they exist precisely because the normal evidence-review pathway hasn't been completed, not because it has. The wider legal logic is explained in unapproved therapeutic goods and their legal basis.

This is relevant to how we read coverage of cannabinoid medicines, some peptides, and emerging phytomedicines. When a substance is available through the SAS or via an Authorised Prescriber, that access pathway is sometimes framed in public coverage as though it signals approval or proven efficacy. It doesn't. The two things are legally and scientifically distinct.

The particular problem in the cannabinoid and peptide space

A lot of the compounds covered on this site sit somewhere on the investigational spectrum. Cannabidiol has one of the stronger evidence bases among cannabinoids, with at least one TGA-approved product in a specific indication. But many of the compounds we write about, lesser-studied cannabinoids, various terpenes, newer peptide classes, are genuinely early-stage investigational, with the weight of evidence sitting in cell studies and animal models rather than randomised controlled trials in humans.

Preclinical data is not nothing. It tells us about mechanisms, about receptor interactions, about pharmacokinetics in model organisms. But it is a different category of evidence to human trial data, and human trial data at Phase II is a different category to a completed Phase III programme. Collapsing those categories, treating a rat study as though it predicts human outcomes, is one of the most common ways science communication goes wrong. We unpack that gap in preclinical vs clinical research.

I'll be direct about something: I think the cannabis and wellness media space has a genuine problem with this. Not because the people writing in it are dishonest, but because "investigational" and "promising early results" get translated into something that sounds much closer to "established" than the evidence warrants. That translation serves commercial interests, sometimes, but I don't think it's usually calculated. It's more often just enthusiasm, and enthusiasm, as any statistician will tell you, is a confounder.

For peptides specifically, the TGA has been increasingly active in enforcement around unapproved compounds. The supply of many peptides marketed for performance or anti-ageing purposes without TGA approval is illegal in Australia, full stop. That's a separate but related point: investigational status doesn't mean unregulated. In some cases it means the opposite; the compound sits in a tightly controlled category precisely because its risk/benefit profile hasn't been established at a regulatory level. The rules on how such products may be described are covered in advertising rules for therapeutic goods.

Reading "investigational" in the wild: a short field guide

When you see the word in a study abstract, press release, or news article, here are the questions worth asking:

• What phase is the research at? A Phase I safety study and a completed Phase III efficacy trial are both "investigational." They are not equivalent.
• Is this in humans, animals, or cell cultures? In vitro and in vivo animal data are hypothesis-generating, not hypothesis-confirming for human outcomes.
• Who funded the study? Investigator-initiated trials and industry-sponsored trials can both be well-designed, but funding source is relevant context for interpreting results.
• Has the study been peer-reviewed, or is this a preprint? Preprints are useful and legitimate, but they have not been through independent peer review. The conclusions may shift.
• What is the comparison condition? Investigational trials sometimes compare against placebo in populations that would otherwise receive active treatment. The ethics of trial design matters to interpretation.

A few common mistakes are worth naming. One is treating a participant's reported experience as proof of an effect; why anecdotes are not evidence explains why that reasoning fails. Another is reading a headline about "promising" results without checking whether the work involved people at all. A third is assuming that because a trial is registered or ethically approved, its findings are reliable. Approval to run a study is permission to investigate, not a verdict on the result.

None of this makes investigational research unimportant. A well-designed Phase II trial with a clear mechanistic rationale, say, examining how a cannabinoid interacts with the endocannabinoid system via CB1 or CB2 receptors, can be genuinely illuminating. Understanding the mechanism is valuable even before the clinical picture is complete. But the value of that research lives in what it tells us about biology, not in what it authorises anyone to claim about a product.

Holding early evidence with patience

Think of sea swimming. You go in not knowing exactly how the current will run or how your body will respond on a given day. You gather information, you adjust, and you don't assume that one swim tells you everything about the next. Honestly, it's a decent model for reading a research pipeline. Early data is the current, worth paying attention to, not something to bet everything on.

The short version is this: "investigational" is a marker of where a substance sits in a formal evidence-generation process. It is not a proxy for quality, promise, or proximity to approval. Reading it carefully, asking what phase, what population, what comparator, what regulator, is a small habit that will save you from a lot of misplaced certainty.

Sources

• Clinical Trials in Australia: Overview, Therapeutic Goods Administration (TGA)
• Clinical development success rates for investigational drugs, Nature Biotechnology / PubMed Central (NIH)
• Unapproved Therapeutic Goods: Regulatory Framework; Therapeutic Goods Administration (TGA)
• Special Access Scheme, Australian Government Department of Health and Aged Care

Hannah Bui, Evidence & Research Literacy Writer