TP-0903

Description:

IC50: 0.027 μM against AXL

AXL and other TAM family members are known to be involved in maintaining the mesenchymal phenotype in cancer cells. Mesenchymal cells have increased invasion and migratory properties, enhanced cell survival in stressed environments, as well as increased resistance to targeted therapies. TP-0903 is a potent anti-cancer agent targeting the AXL receptor tyrosine kinase.

In vitro: On the basis of the potency of TP-0903 in biochemical assays, its activity in cell-based studies was evaluated. TP-0903 showed extremely potent activity in cell viability assays against the pancreatic cancer cell line PSN-1. More importantly, TP-0903 was evaluated for its ability to block GAS6-mediated activation of AXL in pancreatic cancer cells. PSN-1 cells were serum-starved and then stimulated with GAS6 in the presence of various concentrations of TP-0903 [1].

In vivo: TP-0903 restores sensitivity to erlotinib in cell-based and preclinical animal models of cancer by reversing the mesenchymal phenotype driving resistance [2].

Clinical trial: Up to now, TP-0903 is still in the preclinical development stage.

Reference:
[1] Mollard A, Warner SL, Call LT, Wade ML, Bearss JJ, Verma A, Sharma S, Vankayalapati H, Bearss DJ.  Design, Synthesis and Biological Evaluation of a Series of Novel Axl Kinase Inhibitors. ACS Med Chem Lett. 2011 Dec 8;2(12):907-912.
[2] ToleroPharmaceuticals, Inc–TP-0903.  http://www.toleropharmaceuticals.com/TP-0903.html.

Chronic lymphocytic leukemia cells from ibrutinib treated patients are sensitive to Axl receptor tyrosine kinase inhibitor therapy.[Pubmed:30647852]

Oncotarget. 2018 Dec 14;9(98):37173-37184.

Earlier we have shown the expression of a constitutively active receptor tyrosine kinase Axl in CLL B-cells from previously untreated CLL patients, and that Axl inhibitor TP-0903 induces robust leukemic B-cell death. To explore whether Axl is an effective target in relapsed/refractory CLL patients, we analyzed CLL B-cells obtained from CLL patients on ibrutinib therapy. Ibrutinib-exposed CLL B-cells were treated with increasing doses (0.01- 0.50muM) of a new formulation of high-affinity Axl inhibitor, TP-0903 (tartrate salt), for 24 hours and LD50 doses were determined. Sensitivity of CLL B-cells was compared with known prognostic factors and effect of TP-0903 was also evaluated on Axl signaling pathway in CLL B-cells from this cohort. We detected sustained overexpression of Axl in CLL B-cells from CLL patients on ibrutinib treatment, suggests targeting Axl could be a promising strategy to overcome drug resistance and killing of CLL B-cells in these patients. We found that CLL B-cells from sixty-nine percent of relapsed CLL patients actively on ibrutinib therapy were found to be highly sensitive to TP-0903 with induction of apoptosis at nanomolar doses (TP-0903 treatment effectively inhibited Axl phosphorylation and reduced expression levels of anti-apoptotic proteins (Mcl-1, XIAP) in ibrutinib exposed CLL B-cells. In total, our in vitro preclinical studies showing that TP-0903 is very effective at inducing apoptosis in CLL B-cells obtained from ibrutinib-exposed patients supports further testing of this drug in relapsed/refractory CLL.

TP-0903 inhibits neuroblastoma cell growth and enhances the sensitivity to conventional chemotherapy.[Pubmed:29154838]

Eur J Pharmacol. 2018 Jan 5;818:435-448.

Neuroblastoma (NB) is an embryonal tumor with low cure rate for patients classified as high-risk. This class of NB tumors shows a very complex genomic background and requires aggressive treatment strategies. In this work we evaluated the efficacy of the novel multi-kinase inhibitor TP-0903 in impairing NB cells' growth, proliferation and motility. In vitro studies were performed using cell lines with different molecular background, and in vivo studies were done using the zebrafish experimental model. Our results confirmed a strong cytotoxicity of TP-0903 already at the sub-micro molar concentrations. The observed cytotoxicity of TP-0903 was irreversible and the resulting apoptosis was caspase dependent. In addition, TP-0903 impaired colony formation and neurosphere creation. Depending on the molecular background of the selected NB cell lines, TP-0903 influenced either their capacity to migrate, to complete their cell cycle or both. Likewise, TP-0903 reduced NB cells intravasation in vitro and in vivo. Importantly, TP-0903 showed remarkable pharmacological efficacy not only as a mono-treatment, but also in combination with conventional chemotherapy drugs (ATRA, cisplatin, and VP16) in different types of NB cells. In conclusion, the multi-kinase activity of TP-0903 allowed the impairment of several biological processes required for expansion of NB cells, making them more vulnerable to the conventional chemotherapeutics. Altogether, our results support the eligibility of TP-0903 for further (pre)clinical assessments in NB.

Phenotypic chemical screening using a zebrafish neural crest EMT reporter identifies retinoic acid as an inhibitor of epithelial morphogenesis.[Pubmed:26794130]

Dis Model Mech. 2016 Apr;9(4):389-400.

The epithelial-to-mesenchymal transition (EMT) is a highly conserved morphogenetic program essential for embryogenesis, regeneration and cancer metastasis. In cancer cells, EMT also triggers cellular reprogramming and chemoresistance, which underlie disease relapse and decreased survival. Hence, identifying compounds that block EMT is essential to prevent or eradicate disseminated tumor cells. Here, we establish a whole-animal-based EMT reporter in zebrafish for rapid drug screening, calledTg(snai1b:GFP), which labels epithelial cells undergoing EMT to producesox10-positive neural crest (NC) cells. Time-lapse and lineage analysis ofTg(snai1b:GFP)embryos reveal that cranial NC cells delaminate from two regions: an early population delaminates adjacent to the neural plate, whereas a later population delaminates from within the dorsal neural tube. TreatingTg(snai1b:GFP)embryos with candidate small-molecule EMT-inhibiting compounds identified TP-0903, a multi-kinase inhibitor that blocked cranial NC cell delamination in both the lateral and medial populations. RNA sequencing (RNA-Seq) analysis and chemical rescue experiments show that TP-0903 acts through stimulating retinoic acid (RA) biosynthesis and RA-dependent transcription. These studies identify TP-0903 as a new therapeutic for activating RAin vivoand raise the possibility that RA-dependent inhibition of EMT contributes to its prior success in eliminating disseminated cancer cells.

Receptor tyrosine kinase Axl is required for resistance of leukemic cells to FLT3-targeted therapy in acute myeloid leukemia.[Pubmed:26172401]

Leukemia. 2015 Dec;29(12):2382-9.

In acute myeloid leukemia (AML), about 25-30% of patients harbor a constitutively active receptor tyrosine kinase (RTK) FLT3 encoded by a FLT3 allele harboring internal tandem duplication (FLT3-ITD) mutation. The presence of FLT3-ITD correlates with poor prognosis in AML and it makes FLT3 an attractive therapeutic target in AML. Unfortunately, to date small-molecule inhibitors of FLT3 have resulted in only partial and transient clinical responses with residual leukemic blasts resistant to FLT3 inhibitors detected in blood or bone marrow. In this study, we investigated whether the RTK Axl is responsible for resistance of FLT3-ITD(+) AML cells to PKC412 and AC220, FLT3 inhibitors currently under clinical trials for FLT3-ITD(+) AML patients. Upon treatment with PKC412 or AC220, phosphorylation of Axl was significantly enhanced in the FLT3-ITD(+) MV4-11 AML cell line and in primary blasts from a FLT3-ITD(+) AML patient. Consistently, a PKC412-resistant AML cell line and PKC412-resistant primary blasts from FLT3-ITD(+) AML patients had significantly higher levels of constitutively phosphorylated Axl and total Axl when compared with a PKC412-sensitive AML cell line and PKC412-sensitive primary blasts from FLT3-ITD(+) AML patients. We also found that resistance of AML cells against the FLT3 inhibitor PKC412 and AC220 was substantially diminished by the inhibition of Axl via a small-molecule inhibitor TP-0903, a soluble receptor Axl fusion protein Axl-Fc or knockdown of Axl gene expression by shRNA. Collectively, our study suggests that Axl is required for resistance of FLT3-ITD(+) AML cells against the FLT3 inhibitor PKC412 and AC220, and that inhibition of Axl activation may overcome resistance to FLT3-targeted therapy in FLT3-ITD(+) AML.

Targeted Axl Inhibition Primes Chronic Lymphocytic Leukemia B Cells to Apoptosis and Shows Synergistic/Additive Effects in Combination with BTK Inhibitors.[Pubmed:25673699]

Clin Cancer Res. 2015 May 1;21(9):2115-26.

PURPOSE: B-cell chronic lymphocytic leukemia (CLL) is an incurable disease despite aggressive therapeutic approaches. We previously found that Axl receptor tyrosine kinase (RTK) plays a critical role in CLL B-cell survival. Here, we explored the possibility of using a high-affinity Axl inhibitor as a single agent or in combination with Bruton's tyrosine kinase (BTK) inhibitors for future clinical trial to treat patients with CLL. EXPERIMENTAL DESIGN: Expression/activation status of other members of the TAM (e.g., Tyro3, Axl, and MER) family of RTKs in CLL B cells was evaluated. Cells were treated with a high-affinity orally bioavailable Axl inhibitor TP-0903 with or without the presence of CLL bone marrow stromal cells (BMSCs). Inhibitory effects of TP-0903 on the Axl signaling pathway were also evaluated in CLL B cells. Finally, cells were exposed to TP-0903 in combination with BTK inhibitors to determine any synergistic/additive effects of the combination. RESULTS: CLL B cells overexpress Tyro3, but not MER. Of interest, Tyro3 remains as constitutively phosphorylated and forms a complex with Axl in CLL B cells. TP-0903 induces massive apoptosis in CLL B cells with LD50 values of nanomolar ranges. Importantly, CLL BMSCs could not protect the leukemic B cells from TP-0903-induced apoptosis. A marked reduction of the antiapoptotic proteins Mcl-1, Bcl-2, and XIAP and upregulation of the proapoptotic protein BIM in CLL B cells was detected as a result of Axl inhibition. Finally, combination of TP-0903 with BTK inhibitors augments CLL B-cell apoptosis. CONCLUSIONS: Administration of TP-0903 either as a single agent or in combination with BTK inhibitors may be effective in treating patients with CLL.