PF-562271 HCl: Selective ATP-Competitive FAK/Pyk2 Inhibitor for Cancer Research

Executive Summary: PF-562271 HCl is a highly selective, ATP-competitive, and reversible inhibitor of focal adhesion kinase (FAK) and proline-rich tyrosine kinase 2 (Pyk2), exhibiting a low nanomolar IC₅₀ for FAK (1.5 nM) and significant selectivity over other kinases except some CDKs (APExBIO). It demonstrates robust inhibition of tumor proliferation and metastasis in xenograft and transgenic mouse models, with FAK phosphorylation EC₅₀ of 93 ng/mL. PF-562271 HCl is insoluble in water and ethanol but achieves ≥26.35 mg/mL solubility in DMSO with gentle warming. The compound’s utility in cancer research is supported by recent studies linking FAK/Pyk2 inhibition to modulation of tumor microenvironments and pre-metastatic niche formation (Adams et al., 2025). Its stability is optimal at −20°C, and it is widely deployed in mechanistic and translational oncology workflows.

Biological Rationale

Focal adhesion kinase (FAK) and proline-rich tyrosine kinase 2 (Pyk2) are non-receptor tyrosine kinases implicated in signaling pathways governing cell adhesion, migration, proliferation, and survival (Adams et al., 2025). Dysregulation of these kinases is frequently observed in solid tumors, where they enhance tumor cell motility and metastatic potential. FAK signaling orchestrates cytoskeletal dynamics via integrin engagement, while Pyk2 plays a complementary role, especially in cells of hematopoietic origin. Both kinases are central to the establishment and maintenance of the tumor microenvironment (TME), including the recruitment and transformation of myeloid progenitor cells (MPCs) into pro-tumorigenic phenotypes. Modulation of these pathways can disrupt pre-metastatic niche (PMN) formation and tumor progression.

Mechanism of Action of PF-562271 HCl

PF-562271 HCl is an ATP-competitive and reversible inhibitor with high affinity for the kinase domains of FAK (IC₅₀ = 1.5 nM) and Pyk2 (IC₅₀ = 14 nM) (APExBIO). This selectivity enables precise dissection of FAK/Pyk2-driven pathways in cancer models. Upon administration, PF-562271 HCl binds to the ATP-binding pocket of FAK and Pyk2, preventing autophosphorylation at key tyrosine residues (e.g., FAK Y397). The result is rapid suppression of downstream signaling cascades involving PI3K/AKT, MAPK, and Rho GTPases. Inhibition of FAK/Pyk2 activity leads to impaired focal adhesion turnover, reduced cell migration, and induction of apoptosis in tumor cells. In vivo, these effects translate to decreased tumor proliferation and abrogation of metastatic spread, as confirmed in xenograft and transgenic mouse models (Adams et al., 2025).

Evidence & Benchmarks

• PF-562271 HCl exhibits an IC₅₀ of 1.5 nM for FAK and 14 nM for Pyk2 in biochemical kinase assays (APExBIO).
• Shows >100-fold selectivity over other protein kinases, except some cyclin-dependent kinases (CDKs) (APExBIO).
• Inhibits FAK phosphorylation in tumor tissue with an EC₅₀ of 93 ng/mL in mouse models (Adams et al., 2025).
• Suppresses xenograft tumor proliferation and metastasis in a dose-dependent manner (Adams et al., 2025).
• Soluble at ≥26.35 mg/mL in DMSO with gentle warming, but insoluble in water and ethanol (APExBIO).
• Stability is optimal at −20°C under anhydrous conditions (APExBIO).
• Recent clinical research demonstrates that FAK/Pyk2 blockade disrupts PMN formation and tumor-supportive microenvironments (Adams et al., 2025).

Applications, Limits & Misconceptions

PF-562271 HCl is extensively used in cancer biology to interrogate the role of FAK and Pyk2 in tumor growth, metastasis, and microenvironment modulation. It is a reference tool for evaluating the contribution of non-receptor tyrosine kinases to pre-metastatic niche formation and immune cell recruitment. The inhibitor also serves in phenotypic screens, pathway mapping, and as a comparator in combination therapy studies.

• PF-562271 HCl: Advanced Strategies for Tumor Microenvironment Research focuses on immune signaling and next-generation applications; this article clarifies the quantitative selectivity and in vivo benchmarks of PF-562271 HCl for model selection.
• PF-562271 HCl: Precision FAK/Pyk2 Inhibitor for Advanced Applications details advanced workflows; the present article updates with latest selectivity and solubility data.
• Advancing FAK/Pyk2 Inhibitor Science compares resistance mechanisms; this article expands on storage and handling parameters to optimize reproducibility.

Common Pitfalls or Misconceptions

• PF-562271 HCl is not selective for all kinases and may inhibit some CDKs at higher concentrations; always verify off-target profiles for your assay (APExBIO).
• Compound is insoluble in water and ethanol; improper solvent use results in precipitation or loss of activity.
• FAK/Pyk2 inhibition may not fully recapitulate genetic knockout phenotypes due to pathway compensation.
• Extrapolating murine efficacy directly to human clinical outcomes is not supported; cross-species differences in kinase regulation exist.
• Improper storage above −20°C or in humid conditions leads to degradation and reduced potency.

Workflow Integration & Parameters

PF-562271 HCl (A8345) is supplied as a solid by APExBIO. For experimental use, dissolve in DMSO to achieve concentrations ≥26.35 mg/mL with gentle warming (≤37°C). Stock solutions should be aliquoted, protected from light, and stored at −20°C. For in vitro assays, typical working concentrations range from 10 nM to 1 μM, depending on cell type and endpoint. In vivo, dosing regimens are established based on pharmacokinetics and target occupancy, with dose-dependent suppression of FAK phosphorylation observed at plasma EC₅₀ of 93 ng/mL in murine models (Adams et al., 2025). Always confirm solubility and stability prior to use. For further workflow optimization, consult this article, which explores advanced integration of PF-562271 HCl in FAK pathway investigation, complementing the current focus on selectivity and storage.

Conclusion & Outlook

PF-562271 HCl is a gold-standard tool for dissecting FAK/Pyk2-driven oncogenic pathways and tumor microenvironment dynamics. Its high selectivity, robust in vivo efficacy, and defined handling parameters support reproducible research in cancer biology. The compound continues to inform the design of new strategies for targeting tumor proliferation, metastasis, and pre-metastatic niche formation. Ongoing research will further clarify its translational potential and optimize its application in combinatorial cancer therapies.