Summary Prostate cancer (PCa) is the most commonly diagnosed non-skin cancer in American men. A majority of localized PCa can be effectively managed by radiation and surgery, with a 5-year survival rate of over 99%. However, resistance to frontline treatment inevitably develops, leading to castration-resistant PCa (CRPC), with a median survival of only 4-6 years. EZH2 is a Polycomb group protein that constitutes the Polycomb Repressive Complex 2 (PRC2) along with two other core subunits, SUZ12 and EED. EZH2 is among the most up-regulated genes in CRPC and a well-established therapeutic target. EZH2 depletion leads to cellular senescence and abolishes PCa growth. EZH2, when in the PRC2 complex, methylates histone 3 lysine 27 and several recently reported non-histone substrates, leading to PCa progression. These functions of PRC2-EZH2 could be blocked by enzymatic EZH2 inhibitors, such as EPZ-6438. However, enzymatic EZH2 inhibitors have limited growth- inhibitory effects in PCa. Accordingly, recent studies have revealed the non-enzymatic roles of EZH2 in activating target genes such as AR. This function is independent of PRC2 and is rather mediated by coactivators such as P300 and c-Myc. A number of PROTACs have been recently developed, hoping to degrade all EZH2 proteins. Unfortunately, these PROTACs remained largely ineffective, as they were mostly derived from enzymatic EZH2 inhibitors, which were shown only able to bind EZH2 in the trimeric PRC2 complex and thus unable to degrade non-PRC2 EZH2. Addressing this significantly unaddressed gap, we propose to develop a series of PROTACs using the first small molecule that we have identified that binds isolated EZH2 protein (solo EZH2). We propose that these solo-EZH2 PROTACs will degrade newly synthesized EZH2 proteins, ultimately disassociating all EZH2 complexes and fully blocking EZH2 functions. We will test their targets and efficacy in PCa models. We will also use the PROTACs to dissect out the catalytic and non-catalytic roles of EZH2 in various stages of PCa. Ultimately, we will optimize lead compounds in terms of favorable pharmacokinetics and toxicity profiles, having a significant and near-term impact on the development of new treatment strategies for prostate and other cancers.