CRISPR Therapeutics And Vertex Report 36-Month Casgevy Data Confirming Durable Sickle-Cell Disease Cure

CRISPR Therapeutics and Vertex Pharmaceuticals presented 36-month follow-up data from the pivotal CLIMB-121 trial of Casgevy (exagamglogene autotemcel) at the European Haematology Association Annual Congress in Milan on Monday — confirming that 96.4% of sickle-cell disease patients treated with the gene-editing therapy remained free from vaso-occlusive crises across the 36-month observation window, with no late-emerging safety signals and a durable elevation of foetal haemoglobin levels consistent with a functional cure for the majority of treated patients.

The 36-month CLIMB-121 data, presented by trial principal investigator Professor Alexis Thompson of Northwestern University, covers 110 evaluable sickle-cell disease patients treated with Casgevy — the world's first CRISPR/Cas9-based medicine, approved by the FDA and EMA in December 2023. The principal efficacy endpoint — freedom from severe vaso-occlusive crises for at least 12 consecutive months — was met by 96.4% of evaluable patients across the 36-month window, an increase from the 93.5% rate reported at the 24-month interim analysis. The mean foetal haemoglobin level across the treated cohort was 41.3% at month 36, substantially above the approximately 20% threshold associated with clinical protection from sickle-cell crisis and broadly stable relative to the 12-month and 24-month readings — confirming the durability of the underlying gene-editing effect.

The healthcare-system-and-access context is meaningful. Casgevy's US list price of $2.2 million per treatment — set at launch in early 2024 — has been the principal barrier to the broad patient-access trajectory that the clinical-efficacy data would otherwise support. As of Q1 2026, approximately 340 patients globally have received Casgevy treatment, substantially below the pace that the sickle-cell patient community and the companies had initially projected. The Institute for Clinical and Economic Review (ICER) has maintained its value-based assessment of Casgevy at a price range of $1.5–2.1 million, and the evolving outcomes-based reimbursement frameworks being developed by the Centers for Medicare and Medicaid Services and major commercial payers are expected to substantially expand access across the 2026–2028 window as the durability evidence base matures.

The wider gene-editing-and-cell-therapy competitive context is meaningful. The 36-month Casgevy durability data substantially reinforces the clinical case for CRISPR-based gene editing as a therapeutic modality across the haemoglobinopathy disease area — with direct implications for the competitive positioning of Bluebird Bio's Lyfgenia (lovo-cel, a lentiviral gene-therapy approach to sickle-cell disease), the Beam Therapeutics base-editing programme in early clinical development, and the broader pipeline of CRISPR-based therapies across oncology, immunology, and rare-disease indications. The 36-month durable-cure data is expected to be submitted to the FDA and EMA as supplementary label-extension evidence, potentially supporting the companies' reimbursement-negotiation framework.

For investors and operators across the global gene-editing, cell-therapy, and rare-disease-pharmaceutical sectors, the Monday EHA Casgevy 36-month data presentation is the clearest single confirmation that the CRISPR/Cas9 gene-editing modality has delivered on its foundational therapeutic promise at the three-year-durability horizon that payers, regulators, and the patient community have been watching as the critical validation milestone for the platform. The principal forward variable through the rest of the year is the rate of outcomes-based-reimbursement-framework activation across the major US and European payer environments — which will substantially determine whether the 340-patient cumulative treatment base of Q1 2026 accelerates toward the multi-thousand-patient trajectory that the efficacy profile and disease-burden data support.