Ligand Design for ALK-targeting PROTAC^®

Proteolysis targeting chimera (PROTAC^®) is a novel and powerful technology that has been highlighted in the drug discovery and development. It’s a heterobifunctional small molecule containing a ligand for E3 ubiquitin ligase and a ligand for the target protein, thereby resulting in polyubiquitination and subsequent proteasomal degradation of the targeted protein. As a top-ranking supplier in the drug industry, Creative Biolabs is committed to manufacturing therapeutic molecules, peptides, and antibodies for various diseases and has developed one-stop services to accomplish ligand design for PROTAC^®s.

• Introduction to Anaplastic Lymphoma Kinase (ALK)

ALK is a receptor tyrosine kinase (RTK) of the IRK family, which shares a YXXXYY autophosphorylation motif within their activation loops (A-loops). In its native form of the full-length single-chain receptor, ALK is composed of 1620 amino acids. A 1030-residue extracellular region comprises multiple subdomains involving a low-density lipoprotein class A domain (LDL-A), a meprin, A5, mu (MAM) domain, and a glycine (G)-rich domain. The cytoplasmic region encompasses 563 residues and contains a kinase catalytic domain. Ligand binding induces receptor dimerization and activation through trans-autophosphorylation of tyrosine residues within A-loop segments. The phosphorylated sites outside the kinase domain A-loop serve as docking sites for downstream Src homology 2 (SH2) and phosphotyrosine-binding (PTB) domain-containing effector and adapter proteins in the signal transduction cascade.

Fig.1 Domain architecture of full-length ALK, overall ALK crystal structure, and A-loop details. (Lee, 2010)

The fused format of NPM-ALK has been identified in a number of cancers, including diffuse large B-cell lymphoma (DLBCL), non-small-cell lung cancer (NSCLC), and anaplastic large cell lymphomas (ALCL). The formation of dimers by the amino-terminal segment of ALK fusion proteins results in the excessive activation of the ALK protein kinase domain that takes a key part in the oncogenic process. And many studies indicate that cancer cells harboring ALK fusion protein are addicted to ALK activity, thereby, inhibition of ALK activity can suppress the survival of cancer cells. There are four drugs, crizotinib, ceritinib, alectinib, and brigatinib approved by the FDA for the treatment of ALK-positive NSCLC patients. Nevertheless, the emergence of drug resistance is universal. The latest ALK inhibitors and other targeting strategies are now being developed to neutralize the newly emergent mechanisms of ALK resistance.

Fig.2 ALK signaling. (Holla, 2017)

• Ligand Design Services for ALK at Creative Biolabs

It is known that PROTAC^® technology has been successfully utilized to selective degradation of specific protein targets. It is a heterobifunctional molecule consisting of two ligands, which respectively recruit the E3 ligase and the target protein. To degrade ALK fusion protein, several ALK-PROTAC^® molecules have been generated that composed of one of the ALK inhibitors, such as ceritinib, and a ligand of von Hippel-Lindau E3 ligase. It’s a useful chemical tool for in vivo efficacy studies, laying the foundation for the development of the next generation of ALK-targeting PROTAC^®s.

Fig.3 Synthesis of ALK PROTAC^®s and controls. (Zhang, 2018)

Based on the structural characteristics of ALK and these fusion proteins, Creative Biolabs has established versatile, flexible ligand design platforms for the construction of ALK-targeting PROTAC^®s. Since ALK protein levels aren’t important for viability in mammals, our high-efficiency ALK PROTAC^®s are promising to be new therapeutics with minimal toxicity. Furthermore, there’re diversified modalities of ALK ligand available to be applied in challenging projects, including but not limited to small molecules, peptides, and antibodies, according to clients' requirements.

• Key Benefits
  • Cost-effective ligand design strategies and time-saving proposals that advance your research processes
  • Advanced platforms and facilities enable the profound degradation of ALK protein and other targets
  • Practiced technicians with extensive expertise in drug discovery and challenging PROTAC^® projects

PROTAC^® technology is highlighted in drug discovery which presents an exciting opportunity to regulate proteins in a manner independent of signaling or enzymatic activity. As a reliable supplier in the world, Creative Biolabs is committed to studying the current development of in-depth knowledge and treatment of tumors with ALK alteration. We’d like to provide comprehensive ligand discovery services covering design, synthesis and biological evaluation of novel degraders of ALK-targeting PROTAC^®s. For more details, please don’t hesitate to contact us.

References

1. Lee, C.C.; et al. Crystal structure of the ALK (anaplastic lymphoma kinase) catalytic domain. Biochem J. 2010, 430 (3): 425-437.
2. Holla, V.R.; et al. ALK: a tyrosine kinase target for cancer therapy. Cold Spring Harb Mol Case Stud. 2017, 3(1): a001115.
3. Zhang, C.; et al. Proteolysis targeting chimeras (PROTAC^®s) of anaplastic lymphoma kinase (ALK). Eur J Med Chem. 2018, 151: 304-314.