Are you looking for a simple means to boost the efficiency of gene editing and also to reduce the off-target? Yes, it does exist – in one word: 4-hydroxy Tamoxifen. That’s the HIT-CAS9.
Hybrid drug inducible CRISPR/Cas9 technology, HIT-Cas9
They built a fusion between a mutated human estrogen receptor (ERT2) and the Cas9 endonucelase, which makes the CRISPR Cas9 dependent on 4-hydroxytamoxifen.