To test our (+)-JQ1-SSO conjugates in the HeLa pLuc/705 cell line, we compared their activity to the well-studied SSO, without the 5′ (+)-JQ1 modification. Cells were treated with varying concentration (25-200 nM) of either SSO (unconjugated and (+)-JQ1 modified) for 24-hours and quantified by luminometry, serving as a measure of splice correction and SSO efficacy. Our (+)-JQ1-SSO conjugate showed 2.0, 1.8, 1.9, and 1.7 fold higher splice-switching activity compared to the 20 unconjugated SSO, at 25, 50, 100, and 200 nM respectively (Figure ). Covalent addition of (+)-JQ1 did not significantly increase the toxicity of the SSO at any concentration, relative to its unconjugated form -assessed through total protein production quantified by BCA (SI Figure ) and Cell-Titer Glo (SI Figure ).