Biology subjects

Briseno, K.

Publications and source records attributed to Briseno, K..

2 recordsLinked to original sources

bioRxiv2026

Reprogramming Cas9 PAM Recognition for Allele-Specific Editing

The therapeutic potential of CRISPR-Cas9 genome editing is fundamentally constrained by the requirement for specific short DNA sequences (PAMs) flanking the target site, limiting access to many clinically relevant genomic loci. This stringent PAM requirement is particularly problematic in applications which require precise positioning, such as base editing and allele-specific editing. Although PAM-relaxed variants have expanded the targetable genome, they incur trade-offs in on-target activity, off-target editing, and cleavage kinetics. This highlights an unmet need for variants that are re-targeted to alternative PAMs in order to maintain the specificity and enzymatic performance inherent to stringent dinucleotide PAM recognition. To overcome these limitations, we developed a yeast selection platform to engineering SpCas9 variants with re-specified PAM recognition. Using a clinically relevant Huntingtons disease gene (HTT) SNP as a proof-of-concept target, we engineered variants with reciprocal NGC and NGT PAM selectivity, as a step toward allele-specific editing in a large percentage of Huntingtons disease patients. These yeast-selected SpCas9 variants retained their modified activity across multiple endogenous HEK293T loci, demonstrating that this specificity is robust across diverse genomic contexts. The variants surpassed PAM-broadened variants on their respective on-target PAM while displaying broad loss of activity across alternative PAMs, effectively re-specifying PAM recognition toward a single dinucleotide sequence. Retargeted variants recovered on-target cleavage kinetics approaching that of wild-type SpCas9, even under competing substrate conditions, demonstrating that PAM re-specification can simultaneously restore catalytic efficiency and improve specificity. Beyond NGC and NGT, we leveraged our high-throughput platform to engineer Cas9 with re-specified activity across multiple additional non-canonical PAMs in yeast, further demonstrating its utility as a general and programmable framework for expanding the therapeutic reach of precision genome editing.

molecular biology↗

bioRxiv2026

Development of a Fully Non-Viral 1XX-enhanced BCMA CAR-T Cell Therapy for Multiple Myeloma

Multiple myeloma (MM) is a clonal plasma cell malignancy characterized by bone marrow infiltration, monoclonal immunoglobulin production, and microenvironmental dysregulation that leads to systemic organ damage. The advent of B-cell maturation antigen (BCMA)-directed chimeric antigen receptor (CAR) T-cell therapy has induced unprecedented responses and durability for patients with relapsed/refractory MM. These outcomes are rarely observed with prior salvage strategies, although relapse remains the predominant long-term challenge for most patients. The two currently approved BCMA CAR-T cell products use viral vectors to semi-randomly insert the CAR gene, which results in heterogeneous genomic composition and variability in efficacy, safety, and product consistency. To address these challenges, we integrated targeted CRISPR genome engineering with precise CAR transgene insertion at the T-cell receptor alpha constant (TRAC) locus, 1XX CAR signaling architecture to enhance potency and durability, and non-viral manufacturing with a single-stranded DNA repair template to improve efficiency and yield. This approach confers physiological CAR expression, reduces insertional mutagenesis, and improves persistence by mitigating tonic signaling and exhaustion. Our GMP manufacturing process consistently achieved high CAR integration (37.7-72.7%) and yields across all full-scale runs and met predefined release criteria for identity, purity, safety, and quality. In NSG mouse models of MM, the UCCT-BCMA-1 product exhibited exceptionally potent tumor control, CAR-T cell expansion 100-1000-fold greater than that of lentiviral constructs, and durable clearance of myeloma cells after multiple rechallenges. These findings establish a CRISPR-edited, fully non-viral manufacturing platform for next-generation 1XX-BCMA CAR-T therapies with enhanced persistence, safety, and efficacy. One Sentence SummaryCRISPR-engineered, TRAC-targeted 1XX-BCMA CAR-T therapy with improved safety, potency, and persistence in relapsed and refractory multiple myeloma.

cancer biology↗