How Long Does It Take a Stem Cell Therapy to Go From Lab to Clinic?

A cell therapy that eventually reaches FDA approval typically spends a decade or more moving through preclinical research, an Investigational New Drug (IND) application, three phases of human trials, and a Biologics License Application (BLA) review — and most candidates that enter this pipeline never finish it. Using FDA data and peer-reviewed analyses from Tufts Medical Center's NEWDIGS initiative and the BIO/Informa/QLS industry consortium, this article walks through each stage, shows how long two real approved therapies (Kymriah and Ryoncil) actually took, and explains why "not yet FDA-approved" is a meaningfully different claim than "almost approved."

The Five Stages, Start to Finish

Every legally marketed cell therapy in the United States passes through the same regulatory skeleton: preclinical research in the lab and in animal models, an IND application that allows human testing to begin, Phase 1 trials (safety, typically 20-100 people), Phase 2 trials (early efficacy signals, up to several hundred people), Phase 3 trials (confirmatory efficacy, 300-3,000 people), and finally a BLA that FDA's Center for Biologics Evaluation and Research (CBER) reviews before granting approval. According to FDA's own patient-facing description of this process, roughly 70% of drugs entering Phase 1 advance to Phase 2, about 33% of those advance to Phase 3, and only a minority of Phase 3 candidates ultimately clear the finish line (FDA, "Step 3: Clinical Research," fda.gov). None of this is optional paperwork — each phase exists because an earlier phase of medicine has, historically, either turned out to be unsafe, ineffective, or both.

Preclinical Research: The Years Before the Clock Even Starts

Before a single patient is dosed, developers spend years in laboratory and animal studies characterizing how a cell product behaves, how it should be manufactured consistently at scale, and whether it shows a plausible safety and efficacy signal worth testing in humans. This preclinical period is not standardized in length, but industry timelines commonly describe it as spanning several years on its own, well before the IND is even filed. For cell therapies specifically, this stage is often longer and more expensive than for a conventional small-molecule pill, because manufacturing a living, patient-specific or donor-derived cell product reproducibly is a harder engineering problem than synthesizing a chemical compound.

Clinical Trials: Where Most Cell Therapies Actually Die

Once an IND is cleared, Phase 1 trials run roughly several months to establish a safe dose, Phase 2 trials run from several months up to two years to look for an efficacy signal, and Phase 3 trials run one to four years and enroll hundreds to thousands of patients (FDA, "Step 3: Clinical Research," fda.gov). Historically, cell and gene therapies have failed at high rates in this window, which is part of why "clinical trial" and "approved treatment" are not interchangeable terms — a product can be in an active, legitimate Phase 1 or 2 trial for years and still never reach approval.

Where Cell Therapies Actually Beat the Averages

This is the section where the honest data gets more encouraging, and it deserves that framing. A 2023 analysis from Tufts Medical Center's NEWDIGS FoCUS Project, which tracked essentially every durable cell and gene therapy trial registered on ClinicalTrials.gov from 1988 through 2020, found that CAR-T and TCR cell therapies for blood cancers had roughly a 17% likelihood of approval from Phase 1 entry, versus about 5.3% for oncology drugs generally — roughly three times higher. Orphan (rare-disease) gene therapies fared even better, at roughly 28% likelihood of approval from Phase 1, compared with a much lower all-modality average reported by BIO, Informa Pharma Intelligence, and QLS Advisors in their "Clinical Development Success Rates and Contributing Factors 2011-2020" report (Tufts NEWDIGS, October 2023; BIO/Informa/QLS, 2021). In other words, once a cell or gene therapy is far enough along to be well-characterized and narrowly targeted at a serious, defined disease, it tends to outperform typical drug development — but "outperform" still means the majority of candidates fail, and years of trial data are required to know which ones will succeed.

Two Real Products, Two Real Timelines

Numbers are easier to internalize through actual cases. Kymriah (tisagenlecleucel), the first CAR-T cell therapy and first gene therapy approved in the US, traces to Emily Whitehead's landmark infusion at Children's Hospital of Philadelphia in April 2012; the FDA approved Kymriah for pediatric leukemia on August 30, 2017 — about five years and four months later, and that gap followed years of earlier laboratory and adult-trial work by Carl June's team (CHOP, 2022; FDA approval record, 2017). Ryoncil (remestemcel-L), approved December 18, 2024 as the first mesenchymal stromal cell therapy cleared by the FDA, illustrates how bumpy the regulatory endgame can be even for a real, working product: Mesoblast first submitted its BLA in May 2019, received a Complete Response Letter rejecting it in October 2020, resubmitted in February 2023, was rejected again in August 2023, and only won approval after a third submission in July 2024 — more than five years of BLA review alone, on top of the underlying clinical trials (CGTlive, 2024-2025; FDA approval letter, December 18, 2024).

RMAT and Expedited Pathways: Real Acceleration, Not a Bypass

Congress created the Regenerative Medicine Advanced Therapy (RMAT) designation in the 21st Century Cures Act of 2016 specifically to give promising cell and gene therapies faster FDA interaction, rolling review, and other efficiencies. As of September 30, 2025, only 13 RMAT-designated products had actually reached FDA approval, including Casgevy and Lyfgenia for sickle cell disease (both approved December 8, 2023), Roctavian for hemophilia A (June 29, 2023), and Zevaskyn (April 28, 2025) (FDA, "CBER Regenerative Medicine Advanced Therapy (RMAT) Approvals," fda.gov). This is genuine, meaningful progress — it shows the system can move faster for well-supported candidates — but RMAT accelerates the review of evidence that already exists from real trials; it does not exempt anyone from generating that evidence in the first place.

What This Means When a Clinic Says "Breakthrough"

When a clinic advertises a stem cell treatment as a breakthrough that simply hasn't finished FDA paperwork yet, it's worth asking exactly where in this multi-year, multi-phase pipeline the product actually sits — because "not yet approved" spans an enormous range, from a compound still in mouse studies to a therapy awaiting a decision date after three completed trial phases. A treatment with no registered IND, no completed Phase 3 trial, and no BLA under review is not "almost there"; based on the data above, it is realistically years — and, given typical attrition rates, may never arrive at all.

Bottom Line

If you're evaluating a clinic's claim that its treatment is a "breakthrough" awaiting approval, ask three concrete questions: Does it have an active IND on file with FDA, has it completed (not just started) Phase 3 trials with published results, and has a BLA actually been submitted and accepted for review? A "yes" to all three still typically means one to several more years given real-world review timelines like Ryoncil's five-year, twice-rejected BLA history; a "no" to any of them means the treatment is, at best, in the earliest years of a pipeline that historically has taken cell and gene therapies roughly five to fifteen-plus years from first human trial to market — and where even the best-performing categories (CAR-T, orphan gene therapy) still fail to reach approval most of the time. Marketing language that collapses this distance into "we're just waiting on paperwork" should be treated as a red flag, not a timeline.