This 2018 Chinese review highlighted areas in which CRISPR/Cas9 technology has, is, and could be applied to rewrite epigenetic changes:

“CRISPR/Cas9-mediated epigenome editing holds a great promise for epigenetic studies and therapeutics.

It could be used to selectively modify epigenetic marks at a given locus to explore mechanisms of how targeted epigenetic alterations would affect transcription regulation and cause subsequent phenotype changes. For example, inducing histone methylation or acetylation at the Fosb locus in the mice brain reward region, nucleus accumbens, could affect relevant transcription network and thus control behavioral responses evoked by drug and stress.

Epigenome editing has the potential for epigenetic treatment, especially for the disorders with abnormal gene imprinting or epigenetic marks. Targeted epigenetic silencing or reactivation of the mutant allele could be a potential therapeutic approach for diseases such as Rett syndrome and Huntington’s disease.

Noncoding RNA plays important roles in gene imprinting and chromatin remodeling. CRISPR/Cas9 has been shown to be potential for manipulating noncoding RNA expression, including microRNA, long noncoding RNA, and miRNA families and clusters.

In vivo overexpression of the Yamanaka factors have proven to be able to fully or partially help somatic cells to regain pluripotency in situ. These rejuvenated cells would subsequently differentiate again to replace the lost cell types.”

The last paragraph was described in The epigenetic clock theory of aging as a promising technique:

“To date, the most effective in vitro intervention against epigenetic ageing is achieved through expression of Yamanaka factors, which convert somatic cells into pluripotent stem cells, thereby completely resetting the epigenetic clock.”

The reviewers cited three references for in vivo studies of this technique. Overall, I didn’t see that any of the review’s references were in vivo human studies.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6079388/ “Novel Epigenetic Techniques Provided by the CRISPR/Cas9 System”