Gene Editing Weekly — May 22–29, 2026

This digest covers May 22–29, a full seven-day window. The week's dominant theme is cardiovascular base editing: three independent datasets — one NEJM Phase 1b paper, one Nature Medicine Phase 1 trial, and one NHP preclinical readout at EAS 2026 — landed within 96 hours of each other, making PCSK9 silencing and LDLR upregulation the most data-dense front in the field this week. Secondary signals: CBER installed its fourth acting director since January 2025, a rare AAV-linked pediatric brain tumor appeared in Nature Medicine, and Charles River's CGT manufacturing exit prompted its CEO to warn others may follow.

Three programs, three different sponsors, three different regulatory stages — all publishing cardiovascular base-editing data in the same week at the European Atherosclerosis Society Congress and in peer-reviewed journals. The convergence is not coordinated; it reflects how far the LNP-delivered base-editor field has moved since VERVE-101 was halted for safety in 2024.

VERVE-102 (Eli Lilly, acquired through its ~$1 billion Verve Therapeutics acquisition) is now the lead data asset. The Heart-2 Phase 1b trial enrolled 35 patients with heterozygous familial hypercholesterolemia (HeFH) or early-onset coronary artery disease across six dose cohorts (0.3–1.0 mg/kg). At the highest dose (n=7), a single intravenous infusion reduced PCSK9 protein by 88% and LDL-C by 62%, with effects measured at up to 18 months. 1 No dose-limiting toxicity was observed; the principal adverse events were low-grade infusion reactions and fatigue. Fifteen of the 35 patients have passed 12 months of follow-up. The data were simultaneously published in the New England Journal of Medicine (DOI: 10.1056/NEJMoa2601283). 2 This is the first in vivo base-editing human clinical dataset published in NEJM, a marker the field will reference for years. FDA has granted Fast Track designation; Phase 2 is planned for year-end 2026.

Sekar Kathiresan — Lilly SVP and Verve co-founder — framed the clinical aspiration directly: "The Heart-2 results provide early clinical evidence that a single dose of VERVE-102 may mimic the LDL-C lowering effects of PCSK9 cardioprotective variants, potentially transforming cardiovascular care from chronic management to a one-time treatment." 1 Riyaz Patel (Barts Health / UCL), an investigator, noted that many patients on existing therapies struggle to maintain consistent LDL-C control, and the durability shown here addresses a real clinical gap. 3

YOLT-101, published in Nature Medicine on May 22, ran an independent Phase 1 dose-escalation trial in six HeFH patients (three dose cohorts: 0.2, 0.4, 0.6 mg/kg). 4 At 0.6 mg/kg at 24 weeks: PCSK9 down 74.4%, LDL-C down 52.3%. No Grade 3+ adverse events. The delivery vehicle is also a GalNAc-modified lipid nanoparticle targeting hepatocytes via the asialoglycoprotein receptor — the same basic receptor-targeting strategy as VERVE-102, but developed by a Chinese academic team (communicating authors: Zi Jun Wang, Yuxuan Wu, Taihua Yang, Qiang Xia). The patient numbers are small and dose range narrower, but the mechanistic confirmation is independent.

EDIT-401 (Editas Medicine) takes a structurally different approach: rather than silencing PCSK9, it upregulates the LDL receptor (LDLR) via in vivo CRISPR editing, which simultaneously lowers LDL-C, Lp(a), and ApoB through a unified mechanism. 5 In non-human primates, a single dose produced mean reductions of ≥90% in all three lipoproteins. FDA has provided positive pre-IND feedback on the non-clinical program and CMC plan. Editas plans to file a Clinical Trial Notification (CTN) with Australia's TGA in mid-2026 and targets first-in-human proof-of-concept data by year-end 2026. GLP toxicology at 1.5 mg/kg showed no adverse clinical observations and no hepatic histopathology findings at interim analysis.

The LDLR upregulation mechanism has a clinical argument that PCSK9 silencing cannot make: it simultaneously reduces LDL-C, Lp(a), and ApoB in a correlated fashion, potentially addressing the residual cardiovascular risk that remains even with aggressive LDL-C lowering. Linda Burkly (Editas EVP and Chief Scientific Officer) described this as "the transformative potential of our LDLR upregulation approach to address multiple drivers of cardiovascular risk, including residual risk beyond LDL-C alone." 5

The programs at a glance:

The mechanistic divergence between PCSK9 silencing and LDLR upregulation matters for indication selection. PCSK9 inhibition via antibodies or small molecules is well-validated in patients with gain-of-function PCSK9 mutations — the base-editing versions of this approach offer permanence over PCSK9 inhibitors' monthly dosing. The LDLR upregulation route is more novel: it benefits patients regardless of PCSK9 status and addresses Lp(a) reduction (where no approved therapy currently exists), but has no clinical comparator. The two approaches will likely target overlapping but not identical populations.

Alpha-1 antitrypsin deficiency (AATD) — caused by a single G→A substitution (PiZ allele, E342K in SERPINA1) that simultaneously produces toxic hepatic Z-protein accumulation and deficient lung protease inhibition — has become the most competitively mapped indication in gene editing. CRISPR Medicine News documented five active programs this week, comparing DNA base editing and RNA editing (ADAR) approaches head-to-head. 6

Beam Therapeutics BEAM-302 (adenine base editor, LNP delivery): Phase 1/2 has dosed 29 patients (data cut February 10, 2026); the company is pursuing an accelerated approval pathway and plans to begin enrolling approximately 50 AATD patients with lung disease as a pivotal cohort in H2 2026. Trial investigator John Hurst (University College London) called the data "the era of gene correction as a tool for clinicians." 6 BEAM-302's design corrects the PiZ mutation at its native hepatocyte locus, meaning corrected AAT levels can rise physiologically during infection — a property augmentation therapies cannot replicate.

Wave Life Sciences WVE-006 (ADAR RNA editing, GalNAc-oligonucleotide, subcutaneous): In the RestorAATion-2 trial, the 200 mg every-two-weeks regimen produced 64% total AAT as wild-type M-AAT, with Z-AAT reduced by 71%; the editing effect was durable at least three months after dosing stopped. Wave CMO Christopher Wright framed this against DNA editing's "permanent mutations with unpredictable effects in the human genome." The reversibility argument — that RNA editing can be dose-titrated and discontinued — is the core commercial differentiator for indications where regulatory comfort with permanence is not yet established.

Korro Bio KRRO-111 (ADAR RNA editing): mouse model data showed >90% transcript editing. CEO Ram Aiyar described it as "the highest level of SERPINA1 editing reported to date using RNA editing." 6 Clinical stage not yet reached.

YolTech YOLT-202 (adenine base editor, DNA correction, Shanghai): FDA has granted RMAT designation and orphan drug designation; IND has been cleared for a Phase 2/3 single-dose study. In the investigator-initiated trial, the first two patients treated have achieved AAT levels above the protective threshold with detection of structurally correct protein. 6 YolTech completed a $70 million Series C on May 28 (Endpoints News). 7 The company is now the second to advance an in vivo DNA base editor to pivotal-stage trial after Beam, making it a direct competitive reference point.

Sanofi efdoralprin alfa (recombinant AAT-Fc fusion protein, non-editing): The ElevAATe Phase 2 study showed every-three-weeks dosing maintained functional AAT above the normal threshold on 100% of days, versus 41% on standard-of-care augmentation therapy. This sets a high efficacy bar that editing approaches must match or exceed — and, importantly, shows what "competitive standard of care" looks like at the time any AATD gene editor enters registration studies.

The strategic read for Beam and YolTech is that both are racing toward pivotal cohort decisions against a protein therapy standard-of-care that is itself still being established. Whoever files first with durable functional endpoint data faces a faster FDA path; whoever files second faces a more demanding comparator.

The CGT manufacturing ecosystem sent a structural signal this week. Charles River Laboratories (the world's largest CRO by revenue) sold its cell and gene therapy CDMO unit to GI Partners three months ago, forming Rose BioSolutions. In a May 28 Endpoints News interview, CEO Birgit Girshick said Charles River would likely not be the last manufacturer to exit CGT production. 8 Q1 2026 financials confirmed a $118 million loss on the CDMO and Cell Solutions divestiture ($1.53 per share). Charles River built this business through the 2021 acquisitions of Cognate BioServices and Vigene Biosciences; the five-year exit cycle reflects margin pressure in bespoke CGT manufacturing that has been building since AAV demand softened post-2022. For sponsors with active BLA submissions — Sangamo, REGENXBIO, Intellia — CDMO selection and lot consistency have direct regulatory implications, and the supply base is contracting.

YolTech Therapeutics closed a $70 million Series C on May 28. 7 The AATD program details — RMAT designation, IND clearance for Phase 2/3, first patients above protective AAT threshold — are covered in the AATD section above; the financing brings total capital available to advance both the AATD and cardiovascular programs into U.S. and Chinese clinical trials.

CRISPR Therapeutics announced participation in three June investor conferences (Jefferies June 3, William Blair June 3, Goldman Sachs June 9) and — in the accompanying company presentation — introduced the SyNTase™ platform for the first time publicly. 9 The platform is described as "a novel proprietary platform designed to enable precise, efficient, and scalable gene correction." No mechanistic detail has been disclosed. Given that Casgevy (the first approved CRISPR therapy) is now past its commercial launch phase and CEO Sam Kulkarni has described the company as entering a "second phase," the SyNTase™ disclosure may indicate new modality development — but there is nothing yet to evaluate.

Editas Medicine published Q1 2026 results and announced a proposed public offering on the same day it presented EDIT-401 preclinical data at EAS. 10 Q1 net loss was $25.0 million ($0.26/share); revenue was $2.83 million against a consensus estimate of $5.94 million. 11 The underwritten offering of common stock and warrants — with Cantor Fitzgerald and Wells Fargo as joint bookrunners — drove a 14.1% premarket decline. The two pieces of news (NHP efficacy data and dilutive equity raise) are separable signals: EDIT-401 preclinical results were scientifically strong, while the simultaneous capital raise indicates a cash position that requires attention from investors tracking the company's runway to IND filing.

FDA's Center for Biologics Evaluation and Research (CBER) has now seen four acting directors since January 2025. Karim Mikhail — who spent over 20 years at Merck and then served two years as president and CEO of Amarin Corporation (a cardiovascular biopharmaceutical company) before joining FDA's Office of the Commissioner as senior adviser in 2025 — was appointed acting CBER director around May 20. 12 He replaces Katherine Szarama, who was herself appointed May 1 after Vinay Prasad's April 30 departure. FDA Commissioner Marty Makary and CDER acting director Tracy Beth Høeg also departed in this same period.

The sequencing matters for the gene editing field. Three gene therapy BLAs are currently active or near-active at CBER: Intellia's lonvo-z (rolling BLA started April 27, H2 2026 completion target), Sangamo's ST-920 (rolling BLA underway, cash-constrained), and Dyne's z-rostudirsen (BLA just filed, exon-skipping, non-editing but same review center). Two pending actions — REGENXBIO's RGX-121 CRL appeal and RGX-202's rolling BLA start (Q3 2026) — are also in the queue. Each new CBER director inherits these files mid-stream.

Mikhail's industry background (pharma executive, not academic or career FDA) sets him apart from his predecessors. Capital Alpha analysts described the FDA's current leadership situation as an "unprecedented" and "prolonged" vacuum, noting the difficulty of attracting credible candidates to permanent positions. A LinkedIn comment from Don Fink described Mikhail as a "wild card." The policy implication for single-arm trial design is unresolved: Prasad's regime explicitly opposed single-arm trials in gene therapy (the Passage Bio FTD case — 75% layoffs following FDA's RCT requirement for PBFT02 — is the clearest recent casualty). 13 Whether Mikhail maintains that stance is the highest-impact policy variable currently unresolved for programs planning accelerated approval filings with external-control or single-arm designs. REGENXBIO CEO Curran Simpson stated at the May 20 RBC Capital Markets conference that FDA now has a "new team" reviewing RGX-121's CRL appeal.

Nature Medicine published a report on May 22 describing a rare case of AAV gene therapy-related genomic integration that led to a brain tumor in a child. 14 The original NEJM paper (Ahrens-Nicklas RC et al., DOI: 10.1056/NEJMoa2601608) described a five-year-old patient who developed a brain tumor four years after receiving AAV-based gene therapy; the tumor was surgically removed. Nature also published a concurrent research highlight on May 21 framing the same case. 15

AAV vectors are generally not considered integrating — the case highlights a rare-but-not-impossible risk that becomes more relevant as patient numbers scale. The Clinical Trial Vanguard editorial "One Cancer Case Is All It Takes" (published May 25) argued that this case exposes the gap between FDA's 15-year monitoring requirements for CAR-T products and the surveillance systems that actually exist in practice. The monitoring implication for in vivo gene editors — which make permanent genomic changes — is more direct than for AAV: the regulatory justification for long-term genomic surveillance in lonvo-z's BLA review and any future base-editing BLA rests partly on this kind of case precedent.

Precision BioSciences (Durham, NC — developer of the ARCUS® genome editing platform based on I-CreI homing endonucleases) presented late-breaking Phase 1/2 data from the ELIMINATE-B trial (NCT06680232) at EASL Congress 2026 on May 27. 16 The data are notable because HBV covalently closed circular DNA (cccDNA) — the persistent intranuclear viral reservoir responsible for HBV chronicity and relapse after nucleoside analogue therapy — has never before been directly cleared in a clinical setting. PBGENE-HBV showed a 10-fold (1-log) reduction in cccDNA transcripts after just two doses of 0.4 mg/kg, with 80% ARCUS-induced indel coverage of residual cccDNA after three doses. All 15 evaluable patients showed significant HBsAg decline across dose levels, with the first patient showing HBsAg declining continuously for over 12 months. No dose-limiting toxicity was observed. FDA has granted Fast Track designation; next data update expected year-end 2026.

The functional biomarker work is also significant: PBGENE-HBV validated pgRNA as a specific serum marker of cccDNA elimination — 100% of patients with detectable pgRNA at baseline achieved durable pgRNA undetectability. This provides a surrogate endpoint for future HBV cure trials that does not require liver biopsy.

BASE Rx (Base Editing Assessment of Somatic Evolution on Therapy) — the fifth spinout from the Wellcome Sanger Institute — uses CRISPR base editing and prime editing to introduce thousands of protein variants in cancer cell models and map drug-resistance mutations at base-pair resolution. 17 Co-founders Matthew Coelho (CRUK Career Development Fellow) and Mathew Garnett (Sanger Group Leader) have demonstrated the ability to program approximately 32,000 variants across 11 proteins in a single MAPK-pathway experiment. The company was selected this week for the Accelerate@Babraham pre-seed program at Babraham Research Campus.

Coelho described the motivation: "It took around 10 years to go from the approval of Imatinib to the approval of a second-line therapy called Ponatinib... That for me is simply an unacceptable situation, which we are trying to change." 17 The company is seeking pharma partnerships and venture investment.

Genethon and Ampersand Biomedicines announced an exclusive research collaboration on May 27 to develop next-generation AAV capsids with enhanced tissue specificity — initially targeting skeletal muscle. 18 Genethon (a French non-profit AAV gene therapy laboratory supported by AFM-Telethon) and Ampersand Biomedicines (a biotech developing cell-selective delivery via the AND ligand platform) are pairing their capsid engineering and targeting expertise; financial terms were not disclosed.

Sartorius opened a new CGT capability center in Freiburg, Germany on May 27, with investment exceeding €140 million, 18,000 square meters of fully GMP-compliant space, and manufacturing capacity for cytokines, growth factors, and cell culture media more than doubled. 18 The timing against Charles River's CDMO exit is a notable contrast: upstream material suppliers (bioprocess equipment, raw materials) are investing in CGT capacity while downstream contract manufacturers are pulling back.

Nature published a feature on May 28 reporting that cardiac gene therapy programs — after years of limited clinical activity — are gaining momentum. 19 Medley Therapeutics (Texas Heart Institute) is running the first-in-human trial of SAV1 gene silencing for heart failure, with the trial starting in June 2026; pig model data showed a 14-percentage-point ejection fraction improvement. Andrew Baker (University of Edinburgh) described the trial as "the first-in-human studies to take regeneration into the clinic." The field carries history — at least 12 papers in cardiac regeneration were retracted due to data fabrication — but the current cohort of approaches (Medley, Tenaya Therapeutics, AskBio) rests on independent datasets.