I recall hearing about 3309 back in 2014 . I did find the following:
A lead candidate, ZEN 3309, is being developed as a next generation pan-selective BET bromo-domain inhibitor, for the treatment of cancer and autoimmune disorders. ZEN 3309 is a BRD4 protein inhibitor targeting several mechanisms of resistance to endocrine therapies in preclinical models of ER+ breast cancers.
Also mentioned in a presentation at EpiCongress 2014, so it's been in the stable for a while.
https://www.zenithepigenetics.com/upload/media_element/16/01/zenith-epigenetics-presentation---epicongress-boston-july-2014.pdf
masila