Gene Editing Weekly — October 3–9, 2026: an in vivo prime editor reaches a patient, Editas clears its first human trial, and Caribou gives up on off-the-shelf CAR-T

The coverage window for this issue is October 3 – October 9, 2026, Eastern Time. Those seven days moved two in vivo editing programs closer to patients, ended one off-the-shelf cell-therapy company's run, and added two sets of clinical data to the November conference calendar. No human gene-editing trial data were published in the window.

Prime Medicine said on October 5 that the first patient had been dosed in the global Phase 1/2 trial of PM577a, an in vivo prime editor for Wilson disease. 1 The company describes PM577a as the first clinical study of an in vivo prime editing therapy. 1 This briefing covered the program's New Zealand authorization in June; what is new is that a person has now received it.

The trial, listed as NCT07748403, is open-label, first-in-human and dose-escalating in adults and adolescents who carry at least one copy of the H1069Q variant of ATP7B. 1 It will start with adults who are clinically stable on standard care. Efficacy measures may include copper efflux measured by 64Cu PET, serum ceruloplasmin, non-ceruloplasmin-bound copper and 24-hour urinary copper, and the study will test whether patients can stop their existing therapy. 1

Wilson disease is a rare disorder of copper transport: loss-of-function variants in ATP7B impair biliary copper excretion, and copper then accumulates in the liver before reaching the brain, kidneys and cornea. 1 Chelators and zinc salts manage the disease but are taken for life and are limited by tolerability and adherence; liver transplant remains the only cure and is constrained by organ supply. 1

PM577a is formulated as a lipid nanoparticle and given as a single intravenous infusion, designed to correct H1069Q, the most prevalent disease-causing allele in North America and Europe. 1 The FDA granted Rare Pediatric Disease designation to PM577, which qualifies a future approval for a priority review voucher. 1 A follow-on candidate aimed at R778L, the most common mutant allele in East Asian populations, is in preclinical development, and initial clinical data are guided to 2027. 1

Dosing is the whole of the news. There is no efficacy or safety readout behind it yet.

Editas Medicine said on October 8 that it had received approval to initiate the Phase 1/2 Strive trial of EDIT-401 in patients with heterozygous familial hypercholesterolemia. 2 The trial has Human Research Ethics Committee approval and completed the clinical trial notification process with Australia's Therapeutic Goods Administration, and it has also been submitted for review in New Zealand. 2 Five sites are planned across the two countries. 2

EDIT-401 works differently from most editing programs aimed at cholesterol. It edits LDLR to raise LDL receptor expression, an upregulation approach, rather than switching a gene off. 2 In non-human primates it produced a mean reduction of about 90% across LDL-C, Lp(a) and ApoB, and new preclinical data show that the roughly 90% LDL-C reduction was maintained over 10 months in an ongoing primate study. 2 Those durability data go to an AHA session on November 8, presented by chief medical officer Dan Ory, who joined Editas in September. 2

Strive has two parts: a single ascending dose, open-label, dose-finding stage, followed by a single-dose, randomised, placebo-controlled expansion. 2 Editas expects initial safety and tolerability data in the first quarter of 2027 and topline results from the dose-finding stage later that year. 2 The clearance covers Australia and, if granted, New Zealand. 2

Companies used the week to announce conference presentations rather than publish data.

CTX310 targets angiopoietin-related protein 3, or ANGPTL3, and is in development for severe hypertriglyceridemia as well as familial hypercholesterolemia and mixed dyslipidemias. 4 The same release lists three in vivo cardiovascular programs delivered by lipid nanoparticle, including CTX321 against lipoprotein(a), alongside CTX460 for alpha-1 antitrypsin deficiency. 4

PBGENE-HBV is a nuclease program designed to eliminate covalently closed circular DNA, the template that keeps chronic hepatitis B infections alive, and it is the first in vivo gene-elimination approach to use repeat lipid nanoparticle dosing in that disease. 3 It holds Fast Track designation and is in the Phase 1 ELIMINATE-B study, which is enrolling in the United States, Europe, Asia and Oceania. 3 The abstract's own framing is the only clinical claim available until the November 8 session.

The FDA's "What's New for Biologics" list carried postings dated inside the window: an approval letter for NUWIQ dated October 7, voluntary lot withdrawals of intravenous and subcutaneous immune globulin posted October 8, a standard operating procedure on PDUFA application payments posted October 8, and the summary basis for the FAYUVI approval posted October 6. 8 None concerns a genome-editing product, so the ledger records no editing approval, complete response letter, advisory committee action, IND clearance or BLA acceptance for the week. 8 The CBER guidance list shows nothing issued in October. 12

Caribou Biosciences said on October 6 that it plans to discontinue further development of its two allogeneic CAR-T programs and to evaluate strategic alternatives for the company, including a merger, acquisition or sale. 5 The programs are vispa-cel for relapsed or refractory B-cell non-Hodgkin lymphoma and CB-011 for relapsed or refractory multiple myeloma. 5 Caribou reported $113.8 million in cash, cash equivalents and marketable securities as of June 30, 2026, engaged Wedbush Securities as its exclusive financial adviser, and said a substantial workforce reduction would be mostly complete in the fourth quarter of 2026. 5

The decision turns on financing, in the company's own account. Chief executive Rachel Haurwitz called it extraordinarily difficult and said the current financing environment for allogeneic CAR-T had made it hard to secure the capital needed to advance the programs responsibly. 5 Vispa-cel had already reached FDA alignment on a Phase 3 design, and in the Phase 1 ANTLER trial it produced overall response rates of 82% and 86% in two cohorts, with complete response rates of 64% and 63%. 6 CB-011 produced a 92% overall response rate and a 91% minimal-residual-disease-negative rate among evaluable patients in its Phase 1 CaMMouflage trial. 6

Both sets of numbers come from single-arm Phase 1 trials, and Caribou's comparison of vispa-cel with approved autologous CAR-T therapies draws on published data rather than a head-to-head study. 6

Caribou is the latest company to leave ex vivo cell therapy this year. ArsenalBio halted all of its ex vivo CAR-T clinical assets and cut about 99 of 127 employees in early September, TScan Therapeutics paused its Phase 3 ALLOHA-2 trial and cut roughly 75% of its workforce the same month, Cellectis exited its allogeneic CAR-T candidates in mid-September, and Bristol Myers Squibb terminated a $380 million manufacturing partnership with Cellares in late August. 6 Each of those decisions was attributed to the same two pressures: the cost and manufacturing complexity of ex vivo cell therapy, and a financing market unwilling to fund it further. 6

Ultragenyx said on October 7 that it had agreed to sell a Rare Pediatric Disease Priority Review Voucher for $210 million. 7 The company received the voucher when the FDA approved GENGLYCOS, its gene therapy for glycogen storage disease type Ia, which this briefing covered in August. 7

Chief financial officer Howard Horn said the sale provides non-dilutive capital to advance the pipeline and supports the company's path to profitability, and noted that GENGLYCOS itself had been funded in part by an earlier voucher sale. 7 The transaction is subject to customary closing conditions, including the expiration of the antitrust waiting period. 7

GENGLYCOS is a gene-addition therapy, which puts it outside the editing platforms this briefing tracks, and the $210 million price tag is the part worth noting: it is what the voucher market currently pays for a rare-disease gene therapy approval. 7

Two preprints appeared in the window. Neither has been peer-reviewed, and the record for each is a title, an author list and a posting date.

Jang, Rodrigues Menezes, Palczewski and Raguram posted "Engineered mRNA-packaging virus-like particles enable efficient and precise mitochondrial base editing in vitro and in vivo" on October 5, 2026 (DOI 10.64898/2026.10.04.756548). 10 The claim sits in the title: virus-like particles engineered to package messenger RNA delivering base editors to mitochondria, with results in cells and in animals. Mitochondria are the awkward compartment for editing because guide RNAs do not readily cross their membranes, which is why the delivery vehicle carries the claim.

Jing and colleagues posted "Prime editing enables high-throughput identification and characterization of selective MutSβ inhibitors" on October 6, 2026 (DOI 10.64898/2026.10.05.755959). 11 MutSβ is a mismatch-repair complex, and the title's claim is that prime editing can be used as a high-throughput screen to find and characterize inhibitors that act selectively on it. The application is unusual: prime editing appears here as a measurement tool rather than as a therapy.

JAMA published a Viewpoint on October 8, 2026 by Emily Packard Dawson and Lainie Friedman Ross titled "The Ethics of Germline Gene Editing, Revisited". 9 The indexed summary describes it as discussing the subject across three applications: basic science, treatment and prevention, and enhancement. 9

The piece is an argument by two authors, published without regulatory or professional-body standing, and it reports no new clinical or policy finding. 9 It is the third germline-editing commentary to appear in three weeks, after a Nature Medicine piece on September 23 and a Trends in Genetics piece on September 30. 9

The programs that advanced this week share one property: they edit cells inside the body. Prime Medicine's PM577a and CRISPR Therapeutics's CTX310 are lipid-nanoparticle-delivered in vivo editors, Editas's EDIT-401 is an in vivo editor cleared for a first human study, and Precision BioSciences's PBGENE-HBV is an in vivo nuclease program whose abstract is already reporting a clinical signal. 12 The program that stopped this week is manufactured outside the patient, and so were the others that stopped this year.

The retreat from ex vivo cell therapy is a statement about manufacturing and capital rather than about efficacy. Caribou's response rates were competitive, and the company said so while stopping. 6 The consequence for readers is a thinner field of listed, independent ex vivo cell-therapy programs, and a clinical-stage editing pipeline whose near-term readouts now sit almost entirely with in vivo delivery.

Two dates matter next. On November 8, The Liver Meeting session will put numbers behind the PBGENE-HBV abstract title, which already discloses durable pgRNA loss in both HBeAg-positive and HBeAg-negative patients. On October 30, applications close for the FDA's Expedited IND pilot, the rolling-review route this briefing covered when it opened on September 15. 8