Research Appraisals
Evidence-based critical appraisals of the latest medical research, systematically evaluated using Oxford CEBM methodology.
Showing 5 appraisals
The New England journal of medicine
Subretinal Gene Therapy for X-Linked Retinoschisis
BACKGROUND: X-linked retinoschisis is a recessive disease characterized by progressive macular degeneration and vision loss due to pathogenic variation in RS1. METHODS: We administered a single subretinal injection of an AAV8 vector containing human RS1 complementary DNA (scAAV8-hRS1) into one eye of patients 5 to 18 years of age who had X-linked retinoschisis. The primary end point was safety during the 52-week period after injection. Secondary end points included the change from baseline to week 52 in the best corrected visual acuity (BCVA), retinal structure (assessed with swept-source optical coherence tomography; SS-OCT), the function of photoreceptor and bipolar cells (assessed with full-field electroretinography), and macular sensitivity to light (assessed with microperimetry). RESULTS: A total of 12 patients were enrolled. The dose-escalation phase included two cohorts of 3 patients each who received scAAV8-hRS1 at a dose of 7.5×1010 or 1×1011 vector genomes. In the dose-expansion phase, 3 additional patients were enrolled in each cohort. Overall, 56 adverse events were reported during the 52 weeks after surgery. No patient was reported to have an adverse event of grade 3 or higher or ocular inflammation. A macular hole in the treated eye was observed at week 1 in 1 patient. The mean increase at week 52 in the BCVA was 10.8 letters among the treated eyes and 2.4 letters among the untreated eyes. SS-OCT imaging showed closure of the macular schisis cavity by week 13 in the treated eye in all 12 patients. The mean change at week 52 in central retinal thickness was -437.7 μm among the treated eyes and -17.2 μm among the untreated eyes; the outer retinal layers in the treated eyes of 9 patients were continuous at week 52. No clinically meaningful changes in the function of photoreceptor and bipolar cells or macular retinal sensitivity were observed in the treated eyes. CONCLUSIONS: In this study of subretinal gene therapy with scAAV8-hRS1 in 12 patients with X-linked retinoschisis, there were no reports of adverse events of grade 3 or higher or ocular inflammation. Further clinical testing of scAAV8-hRS1 is warranted. (Funded by the National Natural Science Foundation of China and others; Chinese Clinical Trial Registry number, ChiCTR2300076682.).
13 June 2026
Read appraisal →Chembiochem : a European journal of chemical biology
Mutant-Initiated Structure-Guided Refinement Enables Second-Generation Compact IscB Genome Editors
Compact RNA-guided nucleases such as IscB represent an attractive foundation for next-generation genome editors, yet their application in mammalian cells has been constrained by suboptimal activity. Here, instead of re-engineering enzymes, we establish a mutant-initiated, structure-guided optimization strategy to generate second-generation high-activity IscB editors. Using AlphaFold3 to model the engineered IscB*-ωRNA-DNA complex, we reveal remodeling of the nucleic-acid-binding interface induced by activity-enhancing substitutions. Guided by this predicted structure, we perform a focused mutational scan and identify V367 as an activity hotspot. Saturation mutagenesis at this position yields a single substitution, V367Y (IscB*-Act), which increases mean editing efficiency by 34% and achieves up to 2.1-fold improvement across endogenous targets in mammalian cells. Importantly, the V367Y substitution is transferable to an IscB-based adenine base editor, elevating A-to-G conversion by 68% on average and up to 4.46-fold at individual loci without altering the intrinsic editing window. Targeted off-target profiling at loci suggests that V367Y does not substantially increase off-target indels or A-to-G conversion. Together, our work demonstrates a practical framework for second-generation refinement of compact genome editors, bridging deep-learning-enabled structural prediction with interpretable protein engineering, and expands the functional potential of miniature IscB systems for both nuclease and base editing applications.
27 May 2026
Read appraisal →Molecular cell
Rapid customization of base editors via machine learning-powered combinatorial mutagenesis
Being able to control the complementarity and hindrance between target DNA and base editor proteins enables precise, bystander-free editing. Here, we combined combinatorial mutagenesis with machine learning to analyze and engineer these interactions at scale. By profiling DNA motif preferences across 160,000 evoAPOBEC1 and 64 million TadA variants in human cells, we used as little as 0.004% of the mutational landscape to make predictions. This identified variants with motif-specific activity and eliminated residual adenine editing in cytosine base editors. In correcting >800 disease-associated mutations, our variants outperformed previous versions in precluding unintended edits at purine motifs, achieving undetectable bystander edits in 50% of cases. Additionally, a pre-trained, structure-based deep learning model predicted functional TadA variants with 63% success across 2026 variants spanning 26 amino acid sites, without experimental data and in a single prediction round. These approaches streamline the re-engineering of base editors for enhanced precision tailored to specific targets.
23 May 2026
Read appraisal →The New England journal of medicine
Base Editing of HBG1 and HBG2 Promoters for Sickle Cell Disease
BACKGROUND: Sickle cell disease is characterized by chronic hemolytic anemia and recurrent severe vaso-occlusive crises. Ristoglogene autogetemcel (risto-cel) includes autologous CD34+ hematopoietic stem and progenitor cells that have been base-edited to target the HBG1 and HBG2 promoters and inhibit BCL11A binding without altering BCL11A expression, yielding a switch in hemoglobin production from sickle hemoglobin (HbS) to antisickling fetal hemoglobin (HbF). METHODS: In this phase 1-2 study, we enrolled patients 12 to 35 years of age with sickle cell disease who had had at least four severe vaso-occlusive crises in the 2 years before enrollment. After myeloablative conditioning with pharmacokinetically guided administration of busulfan, patients received a single infusion of risto-cel (at a dose of ≥3.0×106 viable CD34+ cells per kilogram of body weight). The primary efficacy end point was freedom from severe vaso-occlusive crises for 12 consecutive months, starting later than 60 days after the last red-cell transfusion. This interim analysis was unplanned; here, we describe safety, editing, engraftment, and hemoglobin production and the number of severe vaso-occlusive crises starting later than 60 days after the last red-cell transfusion. RESULTS: A total of 31 patients received risto-cel and were followed for a mean of 6.6 months (range, 0.3 to 20.4). A median of one cycle (range, one to five) was required for stem-cell collection. Neutrophil engraftment occurred at a median of 17.5 days, and platelet engraftment at a median of 19 days. One patient died from idiopathic pneumonia syndrome. All 31 patients had at least one adverse event, 27 (87%) had an adverse event of grade 3 or higher, and 12 (39%) had a serious adverse event. At 6 months, the mean fraction of on-target edited alleles in peripheral blood was 67.4%, the mean HbF as a fraction of total hemoglobin was more than 60%, and the HbS as a fraction of total hemoglobin was less than 40% (among 13 patients); these levels were maintained throughout follow-up. No investigator-reported severe vaso-occlusive crises occurred later than 60 days after the last red-cell transfusion. CONCLUSIONS: Treatment with risto-cel was followed by rapid engraftment and durable expression of HbF and reduction in HbS. These data support further investigation of risto-cel to treat sickle cell disease. (Funded by Beam Therapeutics; BEACON ClinicalTrials.gov number, NCT05456880.).
12 May 2026
Read appraisal →Blood
Long-term efficacy and safety results of betibeglogene autotemcel gene therapy for transfusion-dependent β-thalassemia.
Betibeglogene autotemcel (beti-cel) gene therapy for transfusion-dependent β-thalassemia (TDT) involves autologous transplantation of hematopoietic stem and progenitor cells transduced with a modified β-globin gene to produce functional adult hemoglobin (Hb) containing βA-T87Q-globin (HbAT87Q). Sixty-three participants with TDT (median age, 17 years [range, 4-35]) received beti-cel in phase 1/2 (n = 22) or phase 3 (n = 41) studies and enrolled in the long-term follow-up LTF-303 study (median follow-up, 5.9 years [range, 2.9-10.1]). Manufacturing refinements in phase 3 increased transduction efficiency, resulting in higher drug product vector copy number and HbAT87Q levels, which translated into higher Hb and transfusion independence (TI) rates than in phase 1/2. TI was achieved by 15 of 22 (68.2%) phase 1/2 participants (median weighted average Hb during TI, 10.2 g/dL) and 37 of 41 (90.2%) of phase 3 participants (median, 11.2 g/dL), and was sustained through last follow-up. Treatment efficacy was similar across ages and TDT genotypes. Among participants achieving TI, 38 of 52 (73%) had discontinued iron chelation at last follow-up, with no increase in liver iron concentration. Markers of ineffective erythropoiesis, including serum transferrin receptor and erythropoietin, improved with restoration of iron homeostasis. Health-related quality-of-life assessment scores showed durable improvements. No malignancies, insertional oncogenesis, or vector-derived replication-competent lentivirus were reported. These findings establish beti-cel as a durable, 1-time therapy that achieves TI, restores iron balance, and improves quality of life, offering a potentially curative treatment option for people with TDT. This trial was registered at www.clinicaltrials.gov as NCT02633943.
11 May 2026
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