In December 2023, Casgevy (exagamglogene autotemcel, exa-cel) became the first CRISPR-based therapy approved by any regulatory authority — licensed simultaneously by the FDA and MHRA for sickle cell disease and transfusion-dependent beta-thalassemia. The clinical data that underpins that approval is extraordinary: in the CLIMB-121 trial, 29 of 29 patients treated with exa-cel became transfusion-free, with a minimum follow-up of 12 months. What happens next is the more interesting question. CRISPR editing has moved past proof-of-concept into a genuine clinical platform, and the 2026 pipeline extends far beyond hemoglobin disorders.
This article is for informational purposes only and does not constitute medical advice. CRISPR-based therapies currently approved or in trials are available only through qualified medical centers. Consult your physician before making any treatment decisions.
Summary
Casgevy (exa-cel) is the only approved CRISPR therapy, with 100% transfusion independence in the CLIMB-121 sickle cell cohort. Intellia's in vivo CRISPR for transthyretin amyloidosis (NTLA-2001) achieved 87% reduction in TTR protein at 12 months — competitive with approved siRNA therapies. The 2026 active pipeline spans hemoglobinopathies, ATTR amyloidosis, Duchenne muscular dystrophy (exon skipping), HIV latent reservoir elimination, and solid tumor CAR-T enhancement. Base editing (single nucleotide changes without double-strand breaks) and prime editing (search-and-replace capability) are entering Phase 1 with improved safety profiles. Over 50 CRISPR trials are actively recruiting globally as of mid-2026.
ClinicalMetric Analysis
- The $2.2 million price tag for Casgevy has become a structural test of whether gene editing can work as a healthcare intervention, not just a scientific one. CRISPR Therapeutics and Vertex set the price below initial analyst estimates, but it remains among the most expensive therapies ever approved. The real access bottleneck isn't price alone — it's the approximately 50 authorized treatment centers globally, each requiring specialized capability for busulfan conditioning, apheresis, and post-infusion monitoring. Patients who could benefit from a one-time cure are unable to access it not because the treatment doesn't exist but because the infrastructure to deliver it doesn't exist near them. This is primarily a healthcare system problem, not a CRISPR problem, but CRISPR will be blamed for it.
- In vivo CRISPR delivered via LNP to the liver is clinically mature. In vivo delivery to non-hepatic tissues is not. Intellia's data for NTLA-2001 (targeting the liver for TTR knockdown) and NTLA-2002 (hereditary angioedema) demonstrate that LNP-mediated liver delivery works with acceptable off-target rates. The liver is easy: it has fenestrated sinusoids that allow LNP extravasation, high vascularization, and natural LNP tropism. Muscle, brain, lung, and tumor tissue don't share these properties. Every in vivo CRISPR program outside the liver is still solving a delivery problem that hasn't been solved at clinical scale.
- Off-target editing anxiety has been disproportionate relative to the clinical evidence to date. The pre-clinical concern — that Cas9 would cut at unintended genomic loci and cause oncogenic mutations — has not materialized in the human data from CLIMB-121 or the Intellia programs, with years of follow-up. This doesn't mean off-target editing is not a risk; it means the risk is lower than the most pessimistic models predicted. Base editing reduces this risk further by avoiding double-strand breaks (which trigger error-prone NHEJ repair). Regulatory agencies now have a more nuanced, data-informed position on off-target risk than they did in 2019. This has accelerated IND approvals for next-generation CRISPR programs.
Casgevy: What the CLIMB Trials Actually Showed
Casgevy uses ex vivo editing of a patient's own hematopoietic stem cells. The mechanism is conceptually clean: sickle cell disease and beta-thalassemia are both caused by defects in the adult beta-globin gene. Fetal hemoglobin (HbF) — silenced after birth by the BCL11A transcription factor — is structurally different and not affected by the sickle mutation. By editing the BCL11A enhancer region in patient HSCs to reduce BCL11A expression, exa-cel reactivates HbF production, compensating for the defective adult hemoglobin.
CLIMB-121 (sickle cell, NCT03745287): 29/29 patients were free of vaso-occlusive crises at 12 months minimum follow-up (median 19.3 months). All patients had HbF levels above 20%, which is the empirical threshold for clinical protection. Prior to treatment, the median annual rate of vaso-occlusive crises was 3.9 per year.
CLIMB-111 (beta-thalassemia, NCT03655678): 42 of 44 patients with non-beta0/beta0 genotype became transfusion-free at 12 months. The 2 who didn't still had significant reduction in transfusion burden.
The safety profile showed the expected toxicities from busulfan conditioning (the myeloablative chemotherapy required to create space for the edited cells), not from the CRISPR editing itself. No off-target editing events with clinical significance have been identified.
In Vivo CRISPR: Intellia's Liver Program
While exa-cel requires ex vivo editing and reinfusion, Intellia Therapeutics has demonstrated that CRISPR can be delivered systemically in lipid nanoparticles to edit cells inside the body — without removing cells from the patient. NTLA-2001 targets transthyretin (TTR), a liver-produced protein that misfolds and deposits in heart and nerve tissue in ATTR amyloidosis.
Phase 1 results published in NEJM showed dose-dependent TTR knockdown: at the highest dose cohort (0.9 mg/kg), serum TTR reduction was 87% at 12 months — maintained without additional dosing. This compares favorably with patisiran (80% TTR reduction, repeated IV infusions) and vutrisiran (80%, quarterly SC injection), both approved siRNA therapies. A single-dose or infrequent-dose CRISPR therapy that achieves comparable efficacy would represent a meaningful improvement in patient burden.
NTLA-2002, also from Intellia, targets KLKB1 for hereditary angioedema — a condition with no known cure. Phase 1/2 data showed 94–95% reduction in attack frequency at the higher doses, with 3 of 6 patients attack-free during the observation period after a single dose. An IND for Intellia's CRISPR program for hemophilia A is now in Phase 1.
Base Editing and Prime Editing: The Next Generation
Standard CRISPR-Cas9 creates a double-strand break (DSB) at the target site, which is then repaired by cellular machinery — imprecisely via NHEJ (creating insertions/deletions) or precisely via HDR (using a donor template). DSBs carry theoretical off-target risk. Two newer approaches avoid DSBs entirely.
Base editing, developed from David Liu's laboratory at the Broad Institute, uses a catalytically impaired Cas9 fused to a deaminase enzyme. It converts one DNA base to another (A→G or C→T) without cutting both strands. Beam Therapeutics and Prime Medicine have base editing programs entering Phase 1/2 for sickle cell, alpha-1 antitrypsin deficiency, and leukemia (anti-CD7 base-edited CAR-T). Base editing is better suited to correcting point mutations — which accounts for a large fraction of monogenic diseases.
Prime editing uses a nickase Cas9 fused to reverse transcriptase and a pegRNA encoding the desired sequence change. It can perform all 12 types of point mutations, small insertions, and small deletions without DSBs or donor templates. Clinical programs are earlier stage — Phase 1 INDs filed in 2025–2026 for rare monogenic diseases. The efficiency gap compared to standard CRISPR has been closing rapidly in preclinical models.
HIV Latency and Duchenne: The Harder Problems
HIV persists in latently infected CD4+ T cells that current antiretroviral therapy cannot eliminate. CRISPR approaches aim to either excise the integrated proviral DNA or disrupt host genes (CCR5, which HIV uses to enter cells) to create HIV-resistant T cells. Sangamo Therapeutics' zinc-finger nuclease program for CCR5 disruption showed detectable engraftment in two patients but has not achieved functional cure. True CRISPR-based HIV eradication — cutting out integrated proviral DNA across the latent reservoir — remains Phase 1 territory, with challenges including the size and diversity of the latent reservoir and delivery to resting CD4+ T cells.
Duchenne muscular dystrophy exon-skipping programs (Solid Biosciences, Sarepta) use AAV-delivered CRISPR to restore a truncated but functional dystrophin reading frame. Early Phase 1 data show detectable dystrophin expression in biopsies, but whether expression levels will be sufficient for clinical benefit in a progressive disease is still being determined.
What CRISPR Trials Are Currently Recruiting
As of mid-2026, the most actively recruiting CRISPR trials on ClinicalTrials.gov include: CLIMB-131 (exa-cel long-term follow-up, NCT04208529); Intellia's NTLA-2001 expanded Phase 2; Graphite Bio's GPH101 for sickle cell (HD-HDR approach, distinct from BCL11A); Editas Medicine EDIT-301 (AsCas12a-based BCL11A editing for sickle cell, NCT04853576); and multiple allogeneic CAR-T programs using CRISPR to delete TRAC and improve persistence. Eligibility for most ex vivo programs requires confirmed genetic diagnosis, age 12 and above, adequate organ function, and ability to tolerate myeloablative conditioning.