Sangamo Biosciences Inc (SGMO)

[jondoeuk]

Seamless ESGCT 2024 (found in a PDF on their site): Highlights

P0670 - Reprogramming Large Serine Recombinases (LSRs) for Site-Specific Integration

Key Points:

Seamless uses a proprietary search motif to identify target sites in almost all coding genes and human safe harbour sites, giving broad applicability beyond sequences similar to natural recombinase targets.

Through directed evolution and rational design, they engineered LSRs to target four selected sites in the human genome.

Engineered LSR clones showed high activity in bacteria, which translated well to human cells.

A leading engineered enzyme, IntSTX-SH2, could precisely integrate DNA into the SH2 locus in human cells.

Optimisation to IntSTX-SH2 2.0 produced a three-fold activity improvement over the first generation, with room for further enhancement.

P0590 - Zinc-Finger Dependent Recombinases (ZFD-Conditional Editing)

Key Points:

Seamless combined Zinc-Finger Binding Domains (ZFDs) with tyrosine recombinases (Y-SSRs) and LSRs.

Engineered variants were inactive without the correct ZFD target site and reactivated only when the site was present, ensuring high specificity.

This strategy increases efficiency and precision of recombinases.

Expands the suite of DNA editing techniques, giving the ability to program edits in a conditional, highly controlled manner.

So Seamless is moving beyond traditional recombinase limits by searching almost all genes for editable sites, programming LSRs to target chosen human sequences, enhancing efficiency via iterations (like IntSTX-SH2 2.0), and increasing specificity with zinc-finger conditional activation.

This positions Seamless with a platform capable of safe, precise, and flexible gene integration, competitive with Sangamo’s MINT, but with greater programmability for new target sites and conditional editing capability (via ZFDs).

All this builds directly on the foundational work described in these papers https://www.nature.com/articles/s41587-023-02121-y https://link.springer.com/article/10.1186/s13059-023-03097-3 https://academic.oup.com/nar/article/51/10/5285/7157522