Induced Protein Degradation (PROTACs)

Controlling Intracellular Protein Levels using Small Molecules

Less than 20% of the proteome has an enzymatic activity. However, current drug development efforts rely heavily on the identification of enzymatic inhibitors, thus ignoring a significant fraction of the proteome.  While RNAi technology theoretically has the potential to address this undruggable proteome, its clinical development has proven challenging.

Our lab is developing different methodologies to address this unmet need.  Specifically, we are interested in affecting different intracellular processes via the small molecule control of protein levels.  These approaches include the development of new proteasome inhibitors and small molecules that disrupt E3 Ubiquitin ligase:substrate interactions to stabilize proteins as well as new methodologies to induce selective protein degradation, such as the recruitment to targeted proteins to E3 ubiquitin ligases or appending hydrophobic tags to the surface of targeted proteins so that the intracellular protein quality control machinery will induce their degradation.

By pharmaceutically controlling protein function via novel mechanisms that do not rely upon enzymatic inhibition, these approaches may allow one to target those proteins that are currently not ‘pharmacologically vulnerable’.

Crews Lab PROTACs timeline

January 10, 2019
Target protein presentation to an E3 ligase is key to PROTAC-mediated degradation specificity

Differential PROTAC substrate specificity dictated by orientation of recruited E3 ligase.

Smith BE, Wang SL, Jaime-Figueroa S, Harbin A, Wang J, Hamman BD, Crews CM.

Nat Commun. 2019 Jan 10;10(1):131. doi: 10.1038/s41467-018-08027-7.

November 28, 2018
Targeting the scaffolding role of a kinase using PROTACs

Addressing Kinase-Independent Functions of Fak via PROTAC-Mediated Degradation.

Cromm PM, Samarasinghe KTG, Hines J, Crews CM.

J Am Chem Soc. 2018 Dec 12;140(49):17019-17026. doi: 10.1021/jacs.8b08008. Epub 2018 Nov 28.

November 19, 2018
Improving potency and selectivity of a TKI via conversion to a PROTAC

Enhancing Antiproliferative Activity and Selectivity of a FLT-3 Inhibitor by Proteolysis Targeting Chimera Conversion.

Burslem GM, Song J, Chen X, Hines J, Crews CM.

J Am Chem Soc. 2018 Dec 5;140(48):16428-16432. doi: 10.1021/jacs.8b10320. Epub 2018 Nov 19.

November 1, 2018
Two heads are better than one: Nutlin-based MDM2-Recruiting BRD4-targeting PROTACs

MDM2-Recruiting PROTAC Offers Superior, Synergistic Antiproliferative Activity via Simultaneous Degradation of BRD4 and Stabilization of p53.

Hines J, Lartigue S, Dong H, Qian Y, Crews CM.

Cancer Res. 2019 Jan 1;79(1):251-262. doi: 10.1158/0008-5472.CAN-18-2918. Epub 2018 Nov 1.

August 2, 2018
An Androgen Receptor (AR)-targeting PROTAC is superior than the Standard of Care Enzalutamide in a murine model of Prostate Cancer

Androgen receptor degradation by the proteolysis-targeting chimera ARCC-4 outperforms enzalutamide in cellular models of prostate cancer drug resistance.

Salami J, Alabi S, Willard RR, Vitale NJ, Wang J, Dong H, Jin M, McDonnell DP, Crew AP, Neklesa TK, Crews CM.

Commun Biol. 2018 Aug 2;1:100. doi: 10.1038/s42003-018-0105-8. eCollection 2018.

June 14, 2018
Addressing a resistance mechanism to a covalent drug using a non-covalent PROTAC

Targeting the C481S Ibrutinib-Resistance Mutation in Bruton’s Tyrosine Kinase Using PROTAC-Mediated Degradation.

Buhimschi AD, Armstrong HA, Toure M, Jaime-Figueroa S, Chen TL, Lehman AM, Woyach JA, Johnson AJ, Byrd JC, Crews CM.

Biochemistry. 2018 Jul 3;57(26):3564-3575. doi: 10.1021/acs.biochem.8b00391. Epub 2018 Jun 14.

November 9, 2017
Turning Promiscuous Ligands into Selective Degraders

Lessons in PROTAC Design from Selective Degradation with a Promiscuous Warhead.

Bondeson DP, Smith BE, Burslem GM, Buhimschi AD, Hines J, Jaime-Figueroa S, Wang J, Hamman BD, Ishchenko A, Crews CM.

Cell Chem Biol. 2017 Nov 9. pii: S2451-9456(17)30354-9. doi: 10.1016/j.chembiol.2017.09.010.

October 25, 2017
First report of PROTAC-mediated degradation of membrane proteins.

The Advantages of Targeted Protein Degradation Over Inhibition: An RTK Case Study.

Burslem GM, Smith BE, Lai AC, Jaime-Figueroa S, McQuaid DC, Bondeson DP, Toure M, Dong H, Qian Y, Wang J, Crew AP, Hines J, Crews CM.

2017 Oct 25. pii: S2451-9456(17)30353-7. doi: 10.1016/j.chembiol.2017.09.009.

September 5, 2017
A system to assess the PROTACability of E3 ligases; can all E3 ligases be hijacked by PROTACs?

Assessing Different E3 Ligases for Small Molecule Induced Protein Ubiquitination and Degradation.

Ottis P, Toure M, Cromm PM, Ko E, Gustafson JL, Crews CM.

ACS Chem Biol. 2017

July 10, 2017
Ligands with micromolar affinities are sufficient to degrade target proteins at nanomolar concentrations when incorporated into PROTACs

Identification and Characterization of Von Hippel-Lindau-Recruiting Proteolysis Targeting Chimeras (PROTACs) of TANK-Binding Kinase 1.

Crew AP, Raina K, Dong H, Qian Y, Wang J, Vigil D, Serebrenik YV, Hamman BD, Morgan A, Ferraro C, Siu K, Neklesa TK, Winkler JD, Coleman KG, Crews CM.

J Med Chem. 2017

June 6, 2016
First report of xenograft tumor regression with VHL-based BET domain-targeting PROTAC


PROTAC-induced BET protein degradation as a therapy for castration-resistant prostate cancer.

Raina K, Lu J, Qian Y, Altieri M, Gordon D, Rossi AM, Wang J, Chen X, Dong H, Siu K, Winkler JD, Crew AP, Crews CM, Coleman KG.

Proc Natl Acad Sci U S A. 2016 113(26):7124-9.

January 12, 2016
Timestamps on the growing PROTAC field


Small-Molecule PROTACS: New Approaches to Protein Degradation.

Toure M, Crews CM.

Angew Chem Int Ed Engl. 2016 55(6):1966-73.


Induced protein degradation: an emerging drug discovery paradigm.

Lai AC, Crews CM.

Nat Rev Drug Discov. 2017 16(2):101-114.

November 23, 2015
First comparison of PROTACs hijacking different E3 ligases; different degradation specificities with VHL- vs.CRBN-based PROTACs targeting BCR-Abl and Abl


Modular PROTAC Design for the Degradation of Oncogenic BCR-ABL.

Lai AC, Toure M, Hellerschmied D, Salami J, Jaime-Figueroa S, Ko E, Hines J, Crews CM.

Angew Chem Int Ed Engl. 2016 55(2):807-10.

June 23, 2015
Controlling intracellular levels of halotag fusion proteins with PROTACs


HaloPROTACS: Use of Small Molecule PROTACs to Induce Degradation of HaloTag Fusion Proteins.

Buckley DL, Raina K, Darricarrere N, Hines J, Gustafson JL, Smith IE, Miah AH, Harling JD, Crews CM.

ACS Chem Biol. 2015 10(8):1831-7




June 10, 2015
First report of a small molecule VHL-based PROTAC; demonstrating the multi-turnover nature of PROTACs


Catalytic in vivo protein knockdown by small-molecule PROTACs.

Bondeson DP, Mares A, Smith IE, Ko E, Campos S, Miah AH, Mulholland KE, Routly N, Buckley DL, Gustafson JL, Zinn N, Grandi P, Shimamura S, Bergamini G, Faelth-Savitski M, Bantscheff M, Cox C, Gordon DA, Willard RR, Flanagan JJ, Casillas LN, Votta BJ, den Besten W, Famm K, Kruidenier L, Carter PS, Harling JD, Churcher I, Crews CM.

Nat Chem Biol. 2015 11(8):611-7.

June 4, 2015
Cereblon hijacked with an ‘all small molecule’ PROTAC; degrading the BET domain protein Brd4


Hijacking the E3 Ubiquitin Ligase Cereblon to Efficiently Target BRD4.

Lu J, Qian Y, Altieri M, Dong H, Wang J, Raina K, Hines J, Winkler JD, Crew AP, Coleman K, Crews CM.

Chem Biol. 2015 22(6):755-63.

May 14, 2013
PhosphoPROTACs: conditional protein degradation dependent on activation of specific signaling pathways


Posttranslational protein knockdown coupled to receptor tyrosine kinase activation with phosphoPROTACs.

Hines J, Gough JD, Corson TW, Crews CM.

Proc Natl Acad Sci U S A. 2013 110(22):8942-7.

September 15, 2008
Inhibiting the growth of breast and prostate tumor cells using ER- and AR-targeting PROTACs


Targeting steroid hormone receptors for ubiquitination and degradation in breast and prostate cancer.

Rodriguez-Gonzalez A, Cyrus K, Salcius M, Kim K, Crews CM, Deshaies RJ, Sakamoto KM.

Oncogene. 2008 27(57):7201-11

July 31, 2008
First ‘all small molecule’ PROTAC; employing nutlin as a MDM2 recruiting moiety


Targeted intracellular protein degradation induced by a small molecule: En route to chemical proteomics.

Schneekloth AR, Pucheault M, Tae HS, Crews CM.

Bioorg Med Chem Lett. 2008 18(22):5904-8. doi: 10.1016/j.bmcl.2008.07.114.

March 31, 2004
First VHL-based PROTACs


Chemical genetic control of protein levels: selective in vivo targeted degradation.

Schneekloth JS Jr, Fonseca FN, Koldobskiy M, Mandal A, Deshaies R, Sakamoto K, Crews CM.

J Am Chem Soc. 2004 126(12):3748-54.

October 2, 2003
First Androgen Receptor and Estrogen Receptor-targeting PROTACs


Development of Protacs to target cancer-promoting proteins for ubiquitination and degradation.

Sakamoto KM, Kim KB, Verma R, Ransick A, Stein B, Crews CM, Deshaies RJ.

Mol Cell Proteomics. 2003 2(12):1350-8.

July 3, 2001
First report of a Proteolysis Targeting Chimera (PROTAC)


Protacs: chimeric molecules that target proteins to the Skp1-Cullin-F box complex for ubiquitination and degradation.

Sakamoto KM, Kim KB, Kumagai A, Mercurio F, Crews CM, Deshaies RJ.

Proc Natl Acad Sci U S A. 2001 98(15):8554-9.



Relevant Reviews

Targeted protein degradation: elements of PROTAC design.
Paiva SL, Crews CM
Curr Opin Chem Biol. 2019 Jun;50:111-119. doi: 10.1016/j.cbpa.2019.02.022. Epub 2019 Apr 17. Review

PROteolysis TArgeting Chimeras (PROTACs) – Past, present and future.
Pettersson M, Crews CM
Drug Discov Today Technol. 2019 Apr;31:15-27. doi: 10.1016/j.ddtec.2019.01.002. Epub 2019 Feb 13. Review

Small-Molecule Modulation of Protein Homeostasis.
Burslem GM, Crews CM
Chemical Reviews. 2017 117(17):11269-11301

Targeted Protein Knockdown Using Small Molecule Degraders.
Raina K, Crews CM
Current Opinion in Chemical Biology. 2017 39:46-53

Targeted Protein Degradation: from Chemical Biology to Drug Discovery.
Cromm PM, Crews CM
Cell Chemical Biology. 2017 24(9):1181-1190

Targeted Protein Degradation by PROTACs.
Neklesa TK, Winkler JD, Crews CM
Pharmacology & Therapeutics. 2017 174:138-144

Waste Disposal- An attractive strategy for cancer therapy
Salami J, Crews CM
Science. 2017 355(6330):1163-1167

Proteolysis-Targeting Chimeras: Induced Protein Degradation as a Therapeutic Strategy
Ottis P, Crews CM
ACS Chemical Biology. 2017 10.1021/acschembio.6b01068

Induced Protein Degradation: An Emerging Drug Discovery Paradigm.
Lai AC, Crews CM
Nature Reviews Drug Discovery. 2017 16:101-114

Targeted Protein Degradation by Small Molecules.
Bondeson DP, Crews CM
Annual Review of Pharmacology and Toxicology. 2017 57:107-123

Small-Molecule PROTACS: New Approaches to Protein Degradation.
Toure M, Crews CM
Angewandte Chemie International Edition. 2016 55:2-10

Small Molecule Control of Intracellular Protein Levels through Modulation of the Ubiquitin Proteasome System.
Buckley DL, and Crews CM
Angewandte Chem. Int. Ed.. 2014 53(9):2312-2330

Chemical biology: Greasy tags for protein removal.
Neklesa TK, Crews CM
Nature. 2012 487(19):308-309

Targeted Intracellular Protein Degradation as a Potential Therapeutic Strategy.
Schneekloth AR and Crews CM
New Frontiers in Chemical Biology: Enabling Drug Discovery (edited by Bunnage ME). 2010

Targeting the Undruggable Proteome: The Small Molecules of My Dreams.
Crews CM
Chemistry & Biology. 2010 17(6):551-555

Chemical inducers of targeted protein degradation.
Raina K, Crews CM
J. Biol. Chem.. 2010 285(15):11057-11060

Design and applications of bifunctional small molecules: why two heads are better than one.
Corson TW, Aberle N, Crews CM
ACS Chemical Biology. 2008 3(11):677-692

Chemical genetic control of protein levels: selective in vivo targeted degradation.
Schneekloth JS Jr., Fonseca F, Koldobskiy M, Mandal A, Deshaies R, Sakamoto K, Crews CM
JACS 2004 126 12 3748-3754