PF-06463922

PF-06463922 is a potent and selective ALK/ROS1 inhibitor with IC50 values ranging from 0.19-0.53 nM for the kinase activity of ROS1 fusion enzymes [1].

The receptor tyrosine kinase c-ros oncogene1 (ROS1) is a receptor with a kinase domain that is related to the anaplastic lymphoma kinase/lymphocyte-specific protein tyrosine kinase (ALK/LTK) and insulin receptor (INSR) RTK families [1].

Via cellular ROS1 autophosphorylation in the recombinant enzyme assay, PF-06463922 showed a 30-fold improved potency against ROS1, compared with crizotinib, ceritinib, alectinib and foretinib (XL-880). Engineered NIH 3T3 cells were expressing oncogenic human ROS1 fusions. In these cells, PF-06463922 was more potent than foretinib and crizotinib by >10 folds, more potent than alectinib and ceritinib by >100 folds against cellular ROS1 autophosphorylation [1].

Oncogenic gene fusions involving the 3' region of ROS1 kinase had been found in various human cancers [2]. Mice bearing CD74-ROS1, CD74-ROS1G2032R and FIG-ROS1(S) s.c. Tumors (250 mm3) were used. Treatments with PF-06463992 at various doses were applied consecutively for 7 or 9 d. At dosages of 0.2 to 1 mg/kg/d, PF-06463922 significantly inhibited the growth of both established FIGROS1(S) and CD74-ROS1 tumors compared with vehicle control. At 2-6 mg/kg/d, PF-06463922 significantly made tumor volumes regress (58–85%, P < 0.0001). In animals bearing NIH 3T3-CD74-ROS1G2032R tumors, treatment with PF-06463922 at 1.0, 3.0, and 10 mg/kg/d significantly inhibited tumor growth by 28%, 44% and 90%, respectively. At 30 mg/kg/d, PF-06463922 made tumor regress by 12%, compared with vehicle [1].

References:
[1].  Zou HY, Li Q, Engstrom LD, et al. PF-06463922 is a potent and selective next-generation ROS1/ALK inhibitor capable of blocking crizotinib-resistant ROS1 mutations. Proceedings of the National Academy of Sciences, 2015, 112(11): 3493-3498.
[2].  Davies KD, Le AT, Theodoro MF, et al. Identifying and targeting ROS1 gene fusions in non–small cell lung cancer. Clinical Cancer Research, 2012, 18(17): 4570-4579.

The ALK inhibitor PF-06463922 is effective as a single agent in neuroblastoma driven by expression of ALK and MYCN.[Pubmed:27483357]

Dis Model Mech. 2016 Sep 1;9(9):941-52.

The first-in-class inhibitor of ALK, c-MET and ROS1, crizotinib (Xalkori), has shown remarkable clinical efficacy in treatment of ALK-positive non-small cell lung cancer. However, in neuroblastoma, activating mutations in the ALK kinase domain are typically refractory to crizotinib treatment, highlighting the need for more potent inhibitors. The next-generation ALK inhibitor PF-06463922 is predicted to exhibit increased affinity for ALK mutants prevalent in neuroblastoma. We examined PF-06463922 activity in ALK-driven neuroblastoma models in vitro and in vivo In vitro kinase assays and cell-based experiments examining ALK mutations of increasing potency show that PF-06463922 is an effective inhibitor of ALK with greater activity towards ALK neuroblastoma mutants. In contrast to crizotinib, single agent administration of PF-06463922 caused dramatic tumor inhibition in both subcutaneous and orthotopic xenografts as well as a mouse model of high-risk neuroblastoma driven by Th-ALK(F1174L)/MYCN Taken together, our results suggest PF-06463922 is a potent inhibitor of crizotinib-resistant ALK mutations, and highlights an important new treatment option for neuroblastoma patients.

PF-06463922, an ALK/ROS1 Inhibitor, Overcomes Resistance to First and Second Generation ALK Inhibitors in Preclinical Models.[Pubmed:26144315]

Cancer Cell. 2015 Jul 13;28(1):70-81.

We report the preclinical evaluation of PF-06463922, a potent and brain-penetrant ALK/ROS1 inhibitor. Compared with other clinically available ALK inhibitors, PF-06463922 displayed superior potency against all known clinically acquired ALK mutations, including the highly resistant G1202R mutant. Furthermore, PF-06463922 treatment led to regression of EML4-ALK-driven brain metastases, leading to prolonged mouse survival, in a superior manner. Finally, PF-06463922 demonstrated high selectivity and safety margins in a variety of preclinical studies. These results suggest that PF-06463922 will be highly effective for the treatment of patients with ALK-driven lung cancers, including those who relapsed on clinically available ALK inhibitors because of secondary ALK kinase domain mutations and/or brain metastases.

Conformational Studies and Atropisomerism Kinetics of the ALK Clinical Candidate Lorlatinib (PF-06463922) and Desmethyl Congeners.[Pubmed:26880581]

Angew Chem Int Ed Engl. 2016 Mar 7;55(11):3590-5.

Lorlatinib (PF-06463922) is an ALK/ROS1 inhibitor and is in clinical trials for the treatment of ALK positive or ROS1 positive NSCLC (i.e. specific subsets of NSCLC). One of the laboratory objectives for this molecule indicated that it would be desirable to advance a molecule which was CNS penetrant in order to treat brain metastases. From this perspective, a macrocyclic template was attractive for a number of reasons. In particular, this template reduces the number of rotatable bonds, provides the potential to shield polar surface area and reinforces binding through a restricted conformation. All of these features led to better permeability for the molecules of interest and thus increased the chance for better blood brain barrier penetration. With a CNS penetrant molecule, kinase selectivity is a key consideration particularly with regard to proteins such as TrkB, which are believed to influence cognitive function. Removal of the chiral benzylic methyl substituent from lorlatinib was perceived as not only a means to simplify synthetic complexity, but also as a strategy to further truncate the molecule of interest. Examination of the NMR of the desmethyl analogues revealed that the compound existed as a mixture of atropisomers, which proved separable by chiral SFC. The individual atropisomers were evaluated through a series of in vitro assays, and shown to have a favorable selectivity profile when compared to lorlatinib. The challenge to develop such a molecule lies in the rate at which the atropisomers interchange dictated by the energy barrier required to do this. Here, we describe the synthesis of the desmethyl macrocycles, conformational studies on the atropisomers, and the kinetics of the interconversion. In addition, the corresponding conformational studies on lorlatinib are reported providing a hypothesis for why a single diastereomer is observed when the chiral benzylic methyl group is introduced.

The ALK/ROS1 Inhibitor PF-06463922 Overcomes Primary Resistance to Crizotinib in ALK-Driven Neuroblastoma.[Pubmed:26554404]

Cancer Discov. 2016 Jan;6(1):96-107.

UNLABELLED: Neuroblastomas harboring activating point mutations in anaplastic lymphoma kinase (ALK) are differentially sensitive to the ALK inhibitor crizotinib, with certain mutations conferring intrinsic crizotinib resistance. To overcome this clinical obstacle, our goal was to identify inhibitors with improved potency that can target intractable ALK variants such as F1174L. We find that PF-06463922 has high potency across ALK variants and inhibits ALK more effectively than crizotinib in vitro. Most importantly, PF-06463922 induces complete tumor regression in both crizotinib-resistant and crizotinib-sensitive xenograft mouse models of neuroblastoma, as well as in patient-derived xenografts harboring the crizotinib-resistant F1174L or F1245C mutations. These studies demonstrate that PF-06463922 has the potential to overcome crizotinib resistance and exerts unprecedented activity as a single targeted agent against F1174L and F1245C ALK-mutated xenograft tumors, while also inducing responses in an R1275Q xenograft model. Taken together, these results provide the rationale to move PF-06463922 into clinical trials for treatment of patients with ALK-mutated neuroblastoma. SIGNIFICANCE: The next-generation ALK/ROS1 inhibitor PF-06463922 exerts unparalleled activity in ALK-driven neuroblastoma models with primary crizotinib resistance. Our biochemical and in vivo data provide the preclinical rationale for fast-tracking the development of this agent in children with relapsed/refractory ALK-mutant neuroblastoma.

PF-06463922 is a potent and selective next-generation ROS1/ALK inhibitor capable of blocking crizotinib-resistant ROS1 mutations.[Pubmed:25733882]

Proc Natl Acad Sci U S A. 2015 Mar 17;112(11):3493-8.

Oncogenic c-ros oncogene1 (ROS1) fusion kinases have been identified in a variety of human cancers and are attractive targets for cancer therapy. The MET/ALK/ROS1 inhibitor crizotinib (Xalkori, PF-02341066) has demonstrated promising clinical activity in ROS1 fusion-positive non-small cell lung cancer. However, emerging clinical evidence has shown that patients can develop resistance by acquiring secondary point mutations in ROS1 kinase. In this study we characterized the ROS1 activity of PF-06463922, a novel, orally available, CNS-penetrant, ATP-competitive small-molecule inhibitor of ALK/ROS1. In vitro, PF-06463922 exhibited subnanomolar cellular potency against oncogenic ROS1 fusions and inhibited the crizotinib-refractory ROS1(G2032R) mutation and the ROS1(G2026M) gatekeeper mutation. Compared with crizotinib and the second-generation ALK/ROS1 inhibitors ceritinib and alectinib, PF-06463922 showed significantly improved inhibitory activity against ROS1 kinase. A crystal structure of the PF-06463922-ROS1 kinase complex revealed favorable interactions contributing to the high-affinity binding. In vivo, PF-06463922 showed marked antitumor activity in tumor models expressing FIG-ROS1, CD74-ROS1, and the CD74-ROS1(G2032R) mutation. Furthermore, PF-06463922 demonstrated antitumor activity in a genetically engineered mouse model of FIG-ROS1 glioblastoma. Taken together, our results indicate that PF-06463922 has potential for treating ROS1 fusion-positive cancers, including those requiring agents with CNS-penetrating properties, as well as for overcoming crizotinib resistance driven by ROS1 mutation.

Lorlatinib (PF-06463922) is a selective, orally active, brain-penetrant and ATP-competitive ROS1/ALK inhibitor. Lorlatinib has Kis of <0.025 nM, <0.07 nM, and 0.7 nM for ROS1, wild type ALK, and ALKL1196M, respectively. Lorlatinib has anticancer activity.

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