2ⁿᵈ Edition of the Cancer R&D World Conference 2026

Abstract

CRISPR-based genome editing has revolutionized drug discovery by uncovering new therapeutic targets. At Tango Therapeutics, we leverage CRISPR-Cas9 to identify synthetic lethal interactions tied to tumor suppressor gene loss, focusing our screenings on advanced human cancer models both in vitro and in vivo.

While large-scale CRISPR screens have successfully been conducted in vitro, expanding this approach to in vivo models presents significant challenges. Issues such as poor sgRNA library representation, low signal-to-noise resolution, inefficient engraftment of transplanted cells, and uneven clonal expansion due to tumor microenvironment heterogeneity all limit the effectiveness of in vivo CRISPR screens. As a result, many of these screens lack the statistical power needed for reliable results, often leading to false positives or negatives, or requiring an excessive number of animals to compensate.

To address these limitations, we applied a cutting-edge CRISPR-based platform called CRISPR-StAR (Stochastic Activation by Recombination)—licensed from IMBA, Vienna—tailored for in vivo screening in CDX models. CRISPR-StAR overcomes traditional hurdles by creating matched pairs of gene knockouts and internal controls within established tumors. This inducible system ensures that screened phenotypes are linked to tumor growth and maintenance rather than tumor formation, making the findings more clinically relevant. Additionally, by capturing each tumor clone’s history through internal controls, CRISPR-StAR significantly reduces noise, enabling more precise data extraction.

Our computational analysis has demonstrated that CRISPR-StAR can achieve a resolution of 1,000 sgRNAs per tumor—reducing animal requirements by 5- to 7-fold compared to conventional methods. Beyond in vivo gene dependency screening, CRISPR-StAR holds promise for tackling other challenging CRISPR screening environments, such as 3D cultures and metastatic models, where non-uniform growth and survival conditions typically introduce high levels of noise. In summary, CRISPR-StAR is paving the way for more efficient, scalable, and clinically relevant in vivo CRISPR screening—bringing us closer to discovering targeted therapies for some of the most complex cancers.