Design,Synthesis And Anti-tumor Activity Of Oral Androgen Receptor Degraders

Androgen receptor(AR),one member of steroid receptors,has been widely studied as the therapeutic target for prostate cancer.Many studies have reported that AR signal pathway is important in the progression of breast cancer.As an AR antagonist,abiraterone can inhibit AR signaling pathway by blocking the synthesis of androgen,which has been used for the treatment of metastatic castration-resistant prostate cancer(CRPC)and breast cancer.Both AR inhibitors Enzalutamide and ARN509 can inhibit AR signaling pathway by inhibiting the binding of androgen to AR,which exhibited a good therapeutic effect on castration-resistant prostate cancer(CRPC)in the clinic.However,the long-term clinical application of these drugs can cause varying degrees of resistance and lead to treatment failure.Therefore,it is still very urgent to explore new therapeutic methods targeting AR.Recently,PROTAC(Proteolysis Targeting Chimeric)is an emerging technology in the field of drug discovery and development,which directly induces the degradation of target proteins through the ubiquitin proteasome sy stem(UPS),and has shown great potential in overcoming drug resistance and targeting non-drugable targets.AR PROTACs have been extensively studied and it has been reported that the cellular activity of AR PROTACs can reach nanomolar or even picomolar levels,but due to the characteristics of PROTACs,their oral bioavailability is generally poor.The AR degrader ARV-110 and ER degrader ARV-471,developed by Arvinas,are the first oral PROTACs that have been publicly reported to enter clinical trials,which is of great significance to the use of PROTAC technology in new drug development.At present,there are still many challenges in the development of PROTACs.The work of this thesis mainly includes the following aspects:(1)Our group have designed and synthesized a series of AR PROTACs based on VHL E3 ligand and explored the efffect of the length and composition of the linker and the binding activity of VHL ligands on the activity of AR PROTACs,giving the best compound ARD-61,which has been selected to explore its biological activities further.(2)Firstly,we explored the activity of ARD-61 in prostate cancer.The data showed that ARD-61 dose and time-dependently induced the degradation of AR in prostate cancer VCaP and LNCaP cells through the ubiquitin proteasome system(UPS)(DC50<5 nM,Dmax>98%).ARD-61 inhibited the proliferation of AR+prostate cancer cells(IC50<5 nM),while had no inhibition effect on AR-prostate cancer cells.And ARD-61 also induced the degradation of AR in VCaP and LNCaP SCID male mice xenograft and inhibited the growth of xenograft tumors.(3)We also explored the activity of AR PROTAC ARD-61 in breast cancer for the first time.ARD-61 induced the degradation of AR in multiple AR+breast cancer cell lines through the proteasome system(DC50<5 nM,Dmax>95%)dose and timedependently.ARD-61 effectively inhibited the proliferation of AR+breast cancer cells but had no inhibitory effect on the proliferation of AR-breast cancer cells.To further explore the possible mechanism of cells growth inhibition induced by ARD-61,we found that ARD-61 induced AR+breast cancer cells G2/M phase cell cycle arrest and/or apoptosis.In addition,ARD-61 inhibited the activation of WNT/β-catenin signaling pathway in AR+breast cancer MDA-MB-453 cells.In vivo data showed that ARD-61 induced the degradation of AR and down-regulated the expression of WNT7B and c-MYC in MDA-MB-453 SCID male mice xenograft.The growth of xenograft tumors was inhibited by ARD-61 without body weight changes.(4)In order to improve the oral bioavailability,we design and synthesized a series of AR PROTACs with CRBN E3 ligands based on the structure of ARD-61.Among these AR PROTACs,ARD-2128 showed better in vitro and in vivo activities and had good oral bioavailability in prostate cancer.We designed,synthesized and evaluation a series of AR PROTACs using VHL E3 ligand and different classes of AR antagonists.Our efforts have resulted in the discovery of exceptionally potent AR degrader ARD-61.And we found that the length,composition of the linker and the binding activity of VHL ligands all have effect on the activity of AR PROTACs.ARD-61 has very potent anti-tumor activity in prostate cancer and achieves low nanomolar DC50 in reducing AR protein in VCaP and LNCaP AR+prostate cancer cell lines and sub-nanomolar IC50 in inhibiting cell growth.We also explored the activity of AR PROTAC ARD-61 in breast cancer for the first time.ARD-61 induces the degradation of AR in multiple AR+breast cancer cell lines through the proteasome system dose and time-dependently and effectively inhibites the proliferation of AR+breast cancer cells.ARD-61 eccectively reduces AR protein in the xenograft tumor tissue in mice and is much more effective in inhibition of tumor growth than Enzalutamide,a FDA-approved AR antagonist,which suggested that AR could be a new potential therapeutic target for the treatment of AR+breast cancer.In the previous work,we achieved exceptionally potent AR degraders using VHL E3 ligand while the oral bioavailability is extremily poor.We designed,synthesized and evaluated a series of cereblon-based AR PROTACs with the objective of discovering potent and orally bioavailable AR degraders.Among these compounds,ARD-2128 has effectively anti-tumor activity both in vitro and in vivo and display excellent pharmacokinetics/pharmacodynamics and oral bioavailability.Our study provides insights into the design of orally bioavailable PROTAC degraders for other protein targets.