Gene Editing Weekly — May 10–17, 2026
ASGCT 2026 week delivered two gene-editing clinical readouts: Vor Biopharma's trem-cel achieved 100% Day-28 engraftment in all 30 AML/MDS patients in a final Phase 1/2a report in Nature Medicine; Fate Therapeutics' FT819 iPSC CAR-T produced 100% SRI-4 response in 3 lupus patients. FDA leadership disruption — Commissioner Makary resigned, CDER director Høeg departed — creates near-term uncertainty for three gene-editing BLAs in progress. Science Translational Medicine published a coordinated prime/base-editing preclinical trio for epilepsy and metabolic disease; NEJM reported the first AAV integration-induced tumor in a human patient.
ASGCT 2026 (Boston, May 11–15) concentrated this week's signal: two gene-editing clinical readouts, new preclinical data from Editas, and a Science Translational Medicine trio on prime and base editing for neurological disorders. At the regulatory level, an FDA Commissioner resigned mid-week and a rolling BLA for a CRISPR therapy moved forward. Below is the full scan.
| Date | Product / Entity | Sponsor | Modality | Event type |
|---|---|---|---|---|
| May 12 | Trem-cel (VOR33) | Vor Biopharma | CRISPR-Cas9 (ex vivo, allo-HCT) | Phase 1/2a final data, Nature Medicine |
| May 11 | FT819 | Fate Therapeutics | CRISPR-edited iPSC CAR-T (ex vivo) | Phase 1 update, ASGCT 2026 |
| May 14 | RGX-121 | REGENXBIO | AAV gene therapy | Partial clinical hold lifted; CRL appeal filed |
| May 14 | ST-920 | Sangamo Therapeutics | ZFP-based gene therapy | Rolling BLA progress (2 modules submitted) |
| May 11 | NGS off-target guidance | FDA (CBER) | Regulatory | Trade press coverage of April 14 draft guidance |
| May 12 | FDA leadership | Makary / Høeg | Regulatory | Commissioner resigned; CDER director departed |
| May 11 | Intellia Q1 2026 | Intellia Therapeutics | CRISPR-Cas9 in vivo | Rolling BLA initiated for lonvo-z (HAE); nex-z Phase 3 resumed |
| May 12 | CRISPR Tx Q1 2026 | CRISPR Therapeutics | CRISPR-Cas9 ex vivo | Casgevy Q1 revenue $43M; >500 patients initiated |
| May 12–13 | Beam Q1 / EHA2026 | Beam Therapeutics | Base editing | Risto-cel BLA year-end 2026; BEAM-302 pivotal H2 2026 |
| May 14 | EDIT-401 | Editas Medicine | CRISPR-Cas12a (in vivo) | Preclinical: ≥90% LDL-C reduction in NHPs, ASGCT 2026 |
| May 13 | STM trio | Multiple | Prime editing / ABE / RNA-LNP | Three papers: epilepsy + metabolic disease models |
| May 13 | AAV tumor case | CHOP / UPenn | AAV gene therapy | NEJM: first confirmed AAV integration tumor in human |
| May 13 | ΨDNA platform | — | Cas12a RNA targeting | Nature Biotechnology: DNA-guided RNA knockdown |
Clinical readouts
Trem-cel in AML/MDS: 100% engraftment, GO maintenance enabled
Vor Biopharma's tremtelectogene empogeditemcel (trem-cel) — a CRISPR-Cas9-edited allogeneic hematopoietic cell transplant with CD33 deleted from donor cells — cleared its primary endpoint in every patient. 1 In the multicenter Phase 1/2a trial (NCT04849910, 30 adults with high-risk CD33+ AML or MDS), all 30 patients achieved neutrophil engraftment by Day 28, with a median time of 10 days (95% CI: 9–10). 1 Median CD33 editing efficiency at manufacture was 90% (range 71–94%).
The mechanistic premise: removing CD33 from donor hematopoietic stem cells converts CD33 into an AML-specific antigen, allowing post-transplant maintenance with gemtuzumab ozogamicin (GO, Mylotarg) without ablating the donor graft. Nineteen patients received GO maintenance; the recommended Phase 2 dose was established at 2 mg/m² every 28 days, and no prolonged high-grade cytopenias were observed during that maintenance — the key safety differentiation versus standard transplant plus GO. 1
Three transplant-related deaths occurred, all after Day 100: one from renal failure attributed to trem-cel combined with adenovirus/cidofovir toxicity, one from sinusoidal obstruction syndrome related to GO, and one from unrelated sepsis. 1 Grade 3+ treatment-emergent adverse events occurred in 90% of patients (anemia 40%, thrombocytopenia 33%, febrile neutropenia 33%). Acute graft-versus-host disease (GvHD) grade 2–4 occurred in 20%; grade 3–4 in 7%. Median relapse-free survival and overall survival were both 14.1 months at a median follow-up of 7.9 months.
Lead investigator John F. DiPersio (Washington University School of Medicine) said the results were encouraging: "We are encouraged by the results of this study showing that a CD33-deleted stem cell transplant looks very similar to the outcomes of standard stem cell transplantation. In the future, we are hopeful we will be able to combine this with CD33-targeted immunotherapies, such as CAR-T cells, and improve treatment options for patients with these very aggressive blood cancers." 2
The trial was halted early for fiscal reasons; this Nature Medicine publication represents the complete final report. Whether Vor Biopharma has the resources to advance a Phase 2 independently — or will require a partner — is the open question following this readout.
FT819 in lupus: conditioning-free CAR-T remodels pathogenic B-cell clones
Fate Therapeutics (San Diego, CA — clinical-stage biotech developing iPSC-derived cell therapies) presented updated Phase 1 data for FT819, its CRISPR-edited off-the-shelf anti-CD19 CAR-T, in moderate-to-severe systemic lupus erythematosus (SLE) at ASGCT 2026. 3 FT819 uses CRISPR to insert the CAR transgene at the TRAC locus and disrupt the TCR bi-allelically, preventing graft-versus-host disease from the iPSC-derived product.
All 3 evaluable patients achieved an SRI-4 response (≥4-point reduction in the SLEDAI composite score without worsening in other domains); 2 of 3 reached lupus low disease activity state (LLDAS). 3 The more granular finding is in the B-cell biology: dominant pathogenic B-cell receptor (BCR) clones were depleted by a mean of 79%, with the effect persisting up to 12 months and the BCR repertoire shifting toward a naïve profile. Earlier data showed 47–73% peripheral B-cell depletion, with secondary lymphoid tissue depletion also confirmed.
Critically, none of the patients received lymphodepleting conditioning chemotherapy — they stayed on background immunosuppression only. No cytokine release syndrome, no ICANS, no GvHD. 3 Dose level 2 (900 million cells) has been initiated.
Three patients is not a readout that settles anything. But the conditioning-free design combined with durable BCR clone depletion at 12 months is the combination that makes this data worth watching — autologous CAR-T trials in autoimmune disease (Kyverna, Bristol Myers Squibb's KYV-101 and obe-cel) have generally required aggressive lymphodepletion to achieve comparable responses.
Note: Two other gene therapy trials reported at ASGCT 2026 this week — Capsida Biotherapeutics' CAP-002 for STXBP1 disorder and Benitec Biopharma's BB-301 for oculopharyngeal muscular dystrophy — are conventional AAV-based gene replacement and silencing therapies without nuclease editing. They fall outside this digest's scope.
FDA & regulatory
REGENXBIO: RGX-121 partial hold lifted; CRL appeal filed
The FDA lifted the partial clinical hold on RGX-121 (clemidsogene lanparvovec), REGENXBIO's investigational AAV9 gene therapy for Mucopolysaccharidosis Type II (MPS II, Hunter syndrome), reported around May 14 via REGENXBIO's Q1 2026 earnings release. 4 Separately, REGENXBIO also filed an appeal of the Complete Response Letter (CRL) FDA issued for RGX-121 in March 2026; the CRL cited study design flaws, specifically the use of external controls and enrollment criteria that made it impossible for FDA to determine whether enrolled patients represented the intended target population. 4 RGX-111, REGENXBIO's program for MPS I (Hurler syndrome), remains under a separate clinical hold. Both programs are partnered with Nippon Shinyaku. REGENXBIO had $150.5M cash as of March 31, 2026, with runway into early 2027.
CEO Curran Simpson indicated the company is simultaneously advancing RGX-202 for Duchenne muscular dystrophy toward a potential BLA submission while continuing FDA engagement on RGX-121. 4
Sangamo: rolling BLA for ST-920 (Fabry disease) continues
Sangamo Therapeutics reported that its rolling BLA submission to FDA for isaralgagene civaparvovec (ST-920), a zinc finger protein (ZFP)-based gene therapy for Fabry disease targeting accelerated approval, had two modules submitted as of May 14. 5 FDA has reaffirmed that 104-week clinical data will be sufficient for the review. Sangamo's cash position of $27.6M funds operations only into Q3 2026, making securing a commercial partner for ST-920 a near-term priority alongside completing the submission.
FDA NGS off-target guidance: comments due July 14
In trade press coverage that ran May 11, the FDA's April 14 draft guidance — "Safety Assessment of Genome Editing in Human Gene Therapy Products Using Next Generation Sequencing" — gained wider attention. 6 The guidance covers on-target edit assessment, off-target editing studies, chromosomal integrity analysis using NGS, and off-target analysis accounting for human genetic variation. It applies to both ex vivo and in vivo products. Comments are due July 14, 2026. Former Commissioner Makary framed the guidance as part of FDA's "forward approach to drive innovation." 6 The practical implication for sponsors: systematic NGS-based off-target characterization — not just targeted PCR — will be expected for IND and BLA submissions.
Near-window context: On April 23, Regeneron's Otarmeni (lunsotogene parvec-cwha) became the first gene therapy for genetic hearing loss (biallelic OTOF variants), approved under the FDA's Commissioner's National Priority Voucher program in 61 days from BLA filing — the first dual AAV vector gene therapy ever approved. 7
FDA leadership: Makary resigned May 12; CDER's Høeg departed May 16
FDA Commissioner Marty Makary, MD, MPH, resigned on May 12, 2026, after 13 months in the role. Dr. Tracy Beth Høeg, director of FDA's Center for Drug Evaluation and Research (CDER), departed on May 16, saying she was fired after declining to resign. Katherine Szarama was named acting director of vaccines and biologics. 8
This matters for the gene editing field specifically: three BLA submissions are either in progress or approaching — Intellia's lonvo-z (rolling, targeting H2 2026 completion), Beam's risto-cel (year-end 2026), and Sangamo's ST-920 (rolling, ongoing). Leadership discontinuity at CBER/CDER typically slows advisory committee scheduling and internal review assignments. The biotech sector's initial read, per multiple analyst notes, is cautiously optimistic that Makary's removal could reduce friction on advisory committee composition — he had removed industry-affiliated members — but the near-term review timeline uncertainty is real.
Corporate moves
Intellia: lonvo-z BLA rolling, nex-z Phase 3 back on track
Intellia Therapeutics (Nasdaq: NTLA) reported Q1 2026 results on May 11 and announced that its rolling BLA for lonvo-z (NTLA-2002) is now underway. 9 Lonvo-z is a CRISPR-Cas9 in vivo gene editing therapy for hereditary angioedema (HAE) that targets the KLKB1 gene in hepatocytes via LNP delivery. The BLA is triggered by Phase 3 HAELO data reported April 27 — outside this window, but the operative driver — showing 87% reduction in HAE attacks versus placebo over weeks 5–28 (p<0.0001, mean monthly attack rate 0.26 vs. 2.10), with 62% of lonvo-z patients entirely attack-free without additional therapy. 9 BLA completion is targeted for H2 2026, with a potential U.S. launch in H1 2027.
CEO John Leonard called it "a historic milestone — the world's first Phase 3 data for an in vivo gene editing candidate." 9 Separately, FDA lifted clinical holds on the MAGNITUDE and MAGNITUDE-2 Phase 3 trials of nex-z (NTLA-2001) for transthyretin amyloidosis (ATTR) in Q1 2026; patient screening has resumed, with MAGNITUDE-2 enrollment completion targeted for H2 2026. Nex-z is developed in collaboration with Regeneron.
Financials: Q1 net loss $96.2M (down from $114.3M in Q1 2025), cash $517.2M plus approximately $207M from an April public offering, funding operations at least into 2028. 9
CRISPR Therapeutics: Casgevy revenue $43M, "second phase" declared
CRISPR Therapeutics (Nasdaq: CRSP) CEO Samarth Kulkarni presented at the Bank of America Securities 2026 Global Healthcare Conference on May 12 and described the company as entering a "second phase" beyond the initial Casgevy launch. 10 Casgevy (exagamglogene autotemcel, developed with Vertex Pharmaceuticals), the CRISPR-Cas9 ex vivo therapy for sickle cell disease (SCD) and transfusion-dependent beta-thalassemia (TDT), generated Q1 2026 revenue of $43M. 10 More than 500 people globally have initiated the Casgevy treatment journey; the therapy is now approved in more than 10 countries covering over 60,000 eligible patients. Approximately 90% of U.S. patients have reimbursed access as of year-end 2025.
Vertex completed the U.S. regulatory submission for Casgevy in children ages 5–11 with SCD or TDT; FDA awarded a Commissioner's National Priority Voucher for this pediatric submission. 10 CRISPR Tx had $2.44B cash as of Q1 (including $585.4M from March 2026 convertible notes), Q1 net loss $122.9M.
Beam Therapeutics: risto-cel BLA targeted year-end, BEAM-302 pivotal cohort H2
Beam Therapeutics (Nasdaq: BEAM — developer of base editing therapies, where adenine or cytosine base editors make precise single-letter DNA changes without double-strand breaks) flagged two milestones this week. First, the company announced EHA2026 (Stockholm, June 11–14) presentations of updated biomarker data from the BEACON Phase 1/2 trial of ristoglogene autogetemcel (risto-cel, formerly BEAM-101), its autologous base-edited cell therapy for SCD. 11 Risto-cel edits the HBG1/2 promoters to re-activate fetal hemoglobin (HbF), mimicking hereditary persistence of fetal hemoglobin. CMO Amy Simon said data continue to show "sickling and rheologic parameters comparable to sickle cell trait." 11 BLA submission is targeted as early as year-end 2026.
Second, Beam became an inaugural industry sponsor of AlphaDetect (a nonprofit under the Alpha-1 Foundation) providing free genetic testing for Alpha-1 Antitrypsin Deficiency (AATD) — a strategic alignment with BEAM-302, Beam's in vivo base-editing liver program for AATD, which has a pivotal cohort planned for H2 2026 with an accelerated approval pathway. 12 Beam's Q1 2026 cash was $1.2B (runway to mid-2029); net loss $94.3M.
Editas: EDIT-401 achieves ≥90% LDL-C reduction in primates
Editas Medicine (Nasdaq: EDIT) presented preclinical data for EDIT-401 at ASGCT 2026 on May 14. 13 EDIT-401 uses an in vivo CRISPR-Cas12a upregulation strategy — rather than knocking out or correcting a gene, it increases LDLR (LDL receptor) expression to lower circulating LDL cholesterol. A single dose achieved ≥90% mean LDL-C reduction across all dose groups in non-human primates (NHPs), durable through approximately 6 months, with only 10–40% functional LDLR allele editing and ≥6-fold increase in hepatic LDLR protein. 13 No adverse clinical observations at the 1.5 mg/kg therapeutic dose. CSO Linda Burkly said the data "strengthen our confidence in EDIT-401 as a potential one-time treatment to deliver meaningful and durable LDL-C lowering." 13 No first-in-human timeline was disclosed; EDIT-401 remains pre-IND.
Papers
Science Translational Medicine: three gene-editing papers for neurological and metabolic disease
Science Translational Medicine (Vol. 18, Issue 849) published three gene-editing therapeutic papers simultaneously on May 13. 141516
SCN1A GEFS+ via prime editing (Kissling et al., University of Zurich): AAV delivery of an intein-split prime editor to neonatal mouse brain ventricles corrected the Scn1a-K1270T pathogenic allele at 34.7±14.5% efficiency in cortical DNA and 81.2±5.9% at the mRNA level. Survival improved from 80% to 100%; heat-induced seizure frequency fell from 78.6% to 13.3% (wild-type: 8%). 14
Dravet syndrome via adenine base editing (Nelson et al.): A dual-AAV9 system delivered an adenine base editor (ABE) targeting the SCN1A R613X nonsense mutation. DNA editing efficiency reached 59%, mRNA editing 97%. 15 Neonatal mouse survival at 45 days was 90% in treated animals versus 27% in untreated controls — a 3.3-fold improvement. Parvalbumin-positive inhibitory neuron excitability and sodium currents were restored to wild-type levels.
Citrullinemia type I via RNA-LNP prime editing (Tálas et al.): An RNA-LNP formulation encoding PE7 prime editor and a synthetic pegRNA corrected the Ass1 fold mutation in neonatal mouse liver at 24% efficiency (single 3 mg/kg dose). All treated animals showed complete normalization of blood ammonia and citrulline concentrations with 100% survival restoration. 16 The RNA-LNP delivery approach is noteworthy because it avoids AAV immunogenicity, allows repeat dosing, and confines editing to the liver.
The publication of all three on the same day reflects an editorial co-submission strategy; the shared theme is using newer editing modalities (prime editing, ABE rather than Cas9 nuclease) in diseases where precision correction of a single pathogenic point mutation is the target.
NEJM: first confirmed AAV integration-induced tumor in a human patient
A case report from Children's Hospital of Philadelphia and the University of Pennsylvania, published in the New England Journal of Medicine on May 13, documents a 5-year-old boy with MPS I (Hurler subtype) who developed a neuroepithelial tumor four years after receiving an AAV9 gene therapy via intracisternal injection. 17 Molecular analysis showed clonal rearrangement of the AAV vector integrated into the PLAG1 proto-oncogene, with expression of a chimeric AAV-PLAG1 transcript. The child's tumor was successfully resected; he maintained MPS I remission and high-level cognitive function post-surgery.
This is the first published clinical case in which AAV vector integration has been confirmed as the mechanism underlying tumor development in a human patient. Prior to this report, insertional oncogenesis had been a theoretical risk — observed in lentiviral gene therapy (X-SCID trials, ~2002–2003) but not confirmed in AAV-treated patients despite more than 6,000 treated individuals in clinical trials. 17 The risk is likely very low in absolute terms, but the PLAG1 integration event will drive discussion of vector integration site analysis requirements — directly relevant to the FDA's April 14 NGS guidance on genome editing safety testing.
Nature Biotechnology: ΨDNA enables DNA-guided Cas12 RNA targeting
A Nature Biotechnology paper describes ΨDNA (pseudo-guide DNA), a synthetic DNA molecule that mimics the crRNA scaffold in reverse orientation and redirects AsCas12a and Cas12i1 to target RNA rather than DNA. 18 In HEK293T cells, AsCas12a-ΨDNA complexes achieved 70–95% knockdown of endogenous transcripts (PPIA, RPL4, PCSK9). The platform also detected clinical hepatitis C virus (HCV) RNA with 100% accuracy across 40 samples. A single effector can be programmed to simultaneously edit DNA and knock down RNA. The clinical translation path is not yet defined, but for the gene therapy field the diagnostic application — point-of-care nucleic acid detection without PCR — is the nearer-term use case.
Ethics & governance
No statements, reports, or guidelines related to gene editing were issued by WHO, UNESCO's International Bioethics Committee, NIH, FDA (beyond the NGS guidance noted above), the UK Human Fertilisation and Embryology Authority, the Nuffield Council on Bioethics, the Hastings Center, or the National Academies of Sciences and Medicine during May 10–17, 2026.
Cover image: Image from Gene-edited stem cell transplant shows promise for aggressive blood cancers
References
- 1
- 2WashU Medicine: Gene-edited stem cell transplant shows promise
medicine.washu.edu
- 3CRISPR Medicine News: FT819 remodels lupus B cells
crisprmedicinenews.com
- 4REGENXBIO Q1 2026 financial results
ir.regenxbio.com
- 5Sangamo Q1 2026 business highlights and financial results
investor.sangamo.com
- 6Big Molecule Watch: FDA draft guidance on gene editing safety testing
bigmoleculewatch.com
- 7
- 8
- 9Intellia Q1 2026 financial results and business updates
ir.intelliatx.com
- 10
- 11Beam Therapeutics: EHA2026 risto-cel presentation announcement
investors.beamtx.com
- 12PRNewswire: Beam Therapeutics supports AlphaDetect
prnewswire.com
- 13Editas Medicine: EDIT-401 preclinical data at ASGCT 2026
ir.editasmedicine.com
- 14
- 15
- 16
- 17
- 18
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