Midostaurin (PKC412)

Midostaurin is an inhibitor of PKC with IC50 values of 22nM, 30nM, 31nM, 24nM, 330nM, 160nM and 1.25μM for PKC-α, PKC-β1, PKC-β2, PKC-γ, PKC-δ, PKC-η and PKC-ε, respectively [1].

Midostaurin is a PKC inhibitor with potent activity against most PKC subtypes. It also has inhibitory activity against KDR and its mouse homologue Flk-1. Other protein kinases involved in angiogenesis, cell cycle and cell growth are not sensitive to midostaurin. Midostaurin shows reversible inhibition of intracellular PKC activity with IC50 value of 0.5μM. Besides PKC, midostaurin inhibits the autophosphorylation of the receptors for PDGF, VEGF and stem cell factor with IC50 values of 80nM, 1μM and 30nM, respectively. Midostaurin also inhibits the FGF-induced c-fos transcription and MAPK activation. Moreover, midostaurin suppresses cell growth of different cell lines through inducing cell cycle arrest in G2/M and inducing apoptosis [1].

Furthermore, midostaurin exerts antitumor activity via inhibiting tumor angiogenesis and proliferation due to its effects on VEGFR and PKC, respectively. Administration of midostaurin prolongs the life span of mice bearing B16 melanoma at dose of 75mg/kg 3 times daily for 9 days [1].

References:
[1] Fabbro D, Buchdunger E, Wood J, et al. Inhibitors of protein kinases: CGP 41251, a protein kinase inhibitor with potential as an anticancer agent. Pharmacology & therapeutics, 1999, 82(2): 293-301.

The DNA Methyltransferase DNMT1 and Tyrosine-Protein Kinase KIT Cooperatively Promote Resistance to 5-Aza-2'-deoxycytidine (Decitabine) and Midostaurin (PKC412) in Lung Cancer Cells.[Pubmed:26085088]

J Biol Chem. 2015 Jul 24;290(30):18480-94.

Lung cancer cells are sensitive to 5-aza-2'-deoxycytidine (decitabine) or Midostaurin (PKC412), because decitabine restores the expression of methylation-silenced tumor suppressor genes, whereas PKC412 inhibits hyperactive kinase signaling, which is essential for cancer cell growth. Here, we demonstrated that resistance to decitabine (decitabine(R)) or PKC412 (PKC412(R)) eventually results from simultaneously remethylated DNA and reactivated kinase cascades. Indeed, both decitabine(R) and PKC412(R) displayed the up-regulation of DNA methyltransferase DNMT1 and tyrosine-protein kinase KIT, the enhanced phosphorylation of KIT and its downstream effectors, and the increased global and gene-specific DNA methylation with the down-regulation of tumor suppressor gene epithelial cadherin CDH1. Interestingly, decitabine(R) and PKC412(R) had higher capability of colony formation and wound healing than parental cells in vitro, which were attributed to the hyperactive DNMT1 or KIT, because inactivation of KIT or DNMT1 reciprocally blocked decitabine(R) or PKC412(R) cell proliferation. Further, DNMT1 knockdown sensitized PKC412(R) cells to PKC412; conversely, KIT depletion synergized with decitabine in eliminating decitabine(R). Importantly, when engrafted into nude mice, decitabine(R) and PKC412(R) had faster proliferation with stronger tumorigenicity that was caused by the reactivated KIT kinase signaling and further CDH1 silencing. These findings identify functional cross-talk between KIT and DNMT1 in the development of drug resistance, implying the reciprocal targeting of protein kinases and DNA methyltransferases as an essential strategy for durable responses in lung cancer.

Phase I/II trial of the combination of midostaurin (PKC412) and 5-azacytidine for patients with acute myeloid leukemia and myelodysplastic syndrome.[Pubmed:25530214]

Am J Hematol. 2015 Apr;90(4):276-81.

We investigated the combination of midostaurin and azacitidine (AZA) in patients with acute myeloid leukemia (AML) and high risk myelodysplastic syndrome (MDS). Patients received AZA 75 mg m(-2) on days 1-7 and midostaurin 25 mg bid (in cohort 1 of phase I) or 50 mg bid (in cohort 2 of Phase I and in Phase II) orally on day 8-21 during the first cycle and continuously thereafter. Fourteen patients were enrolled in the phase I and 40 in the phase II. Overall response rate was 26%. The median remission duration (RD) was 20 weeks and was significantly longer in patients with FLT3 mutations not previously exposed to other FLT3 inhibitors (P = 0.05) and in patients not previously transplanted (P = 0.01). Thirty-two (59%) patients have died, all of complications related to disease progression. G3-4 nonhematological toxicity was reported in 38 (70%) patients, most frequently infections (56%), ejection fraction reduction (11%), and diarrhea or nausea/vomiting (9% each). The combination of midostaurin and AZA is an effective and safe regimen in patients with AML and high-risk MDS. Patients with FLT3 mutations but not previously exposed to other FLT3 inhibitors and patients not previously transplanted derived the greatest benefit. Further studies with this combination are warranted.

Preclinical and phase I results of decitabine in combination with midostaurin (PKC412) for newly diagnosed elderly or relapsed/refractory adult patients with acute myeloid leukemia.[Pubmed:23798029]

Pharmacotherapy. 2013 Dec;33(12):1341-52.

PURPOSE: To determine the preclinical activity, clinical maximum tolerated dose (MTD), and recommended phase II dose of midostaurin (MS) combined either sequentially or concurrently with intravenous decitabine (DAC) in newly diagnosed patients 60 years or older or relapsed/refractory adult patients (18 years or older) with acute myeloid leukemia (AML). PATIENTS AND METHODS: Cultured and primary AML cells were treated with DAC and/or MS and analyzed by flow cytometry and immunoblot analyses. In the phase I study, 16 patients were enrolled; 8 were newly diagnosed patients 60 years or older and 8 were 18 years or older with relapsed AML. Only 2 of 16 patients (13%) had FLT3-internal tandem duplication (ITD) mutations, and no patient had KIT mutations. RESULTS: Compared with treatment with either agent alone, sequential treatment with DAC and MS exerted superior anti-AML activity in cultured and primary FLT3-ITD-expressing AML cells. In the subsequent phase I study, the MTD and schedule of administration of the combination was identified as DAC followed by MS. Three patients developed dose-limiting toxicities: two patients developed pulmonary edema requiring mechanical ventilation and one patient developed a prolonged QTc greater than 500 msec. Based on an intent-to-treat analysis, 57% of the patients achieved stable disease or better while enrolled in the trial; 25% had a complete hematologic response. Pharmacokinetic analysis revealed results similar to those previously reported for MS. CONCLUSION: The in vitro combination of DAC and MS is synergistically active against FLT3-ITD mutations expressing AML cells. In a clinical setting, the combination of sequentially administered DAC followed by MS is possible without significant unexpected toxicity, but the concurrent administration of DAC and MS led to pulmonary toxicity after only a few doses. On the basis of these results, additional studies exploring the sequential combination of untreated AML in elderly patients are warranted to further evaluate this combination at the MTD.

Mast cell leukemia with prolonged survival on PKC412/midostaurin.[Pubmed:25031773]

Int J Clin Exp Pathol. 2014 May 15;7(6):3439-43. eCollection 2014.

Mast cell leukemia (MCL) is a rare and aggressive form of systemic mastocytosis. There are approximately 50 reported cases since 1950s. MCL is refractory to cytoreduction chemotherapy and the average survival is only six months. We report a MCL case in a 71 year-old woman with high tumor load at the initial presentation in 2005, who did not respond to either interleukin-2 or dasatinib therapy. After enrolled in a clinical trial of PKC412 (or Midostaurin) with a daily dose of 100 mg, the patient responded well to PKC412 and became transfusion independent in three months. Since then, her disease had been stably controlled. This is the first report of a high-tumor-load MCL case which achieved prolonged survival (101 months) by PKC 412. The 101-month overall survival is the longest among reported MCL cases in the English literature.

PKC412 induces apoptosis through a caspase-dependent mechanism in human keloid-derived fibroblasts.[Pubmed:15306200]

Eur J Pharmacol. 2004 Aug 23;497(2):155-60.

There is no established pharmacological therapy for skin keloids, a wound healing disorder. In this study, we investigated the effect of N-benzoyl staurosporine (PKC412), a protein kinase C inhibitor, on human keloid-derived fibroblasts to examine whether this agent is applicable for the treatment of keloid formation. Although PKC412 induced apoptosis in keloid fibroblasts in a time- and dose-dependent manner, the effective concentration of this agent was much higher than that of staurosporine. Western blotting showed that both PKC412 (10 microM) and staurosporine (100 nM) cleaved pro-caspase-3 to active forms. An in vitro caspase assay also showed that PKC412 and staurosporine elevated caspase-3 activities. Carbobenzoxy-Val-Ala-Asp-fluoromethyl ketone (Z-VAD-FMK), a caspase inhibitor with a broad spectrum, inhibited caspase-3 activities stimulated by PKC412 and staurosporine; however, only PKC412-induced apoptosis, but not staurosporine-induced apoptosis, was prevented by Z-VAD-FMK. These results suggested that PKC412-induced apoptosis, but not staurosporine-induced apoptosis, is mainly mediated by the caspase-dependent mechanism.

The phosphatidylinositide 3'-kinase/Akt survival pathway is a target for the anticancer and radiosensitizing agent PKC412, an inhibitor of protein kinase C.[Pubmed:11719451]

Cancer Res. 2001 Nov 15;61(22):8203-10.

Activation of the phosphatidylinositol 3'-kinase (PI3K)/Akt survival pathway protects against apoptotic stress stimuli. Therefore, compounds that down-regulate this pathway are of clinical interest for single and combined anticancer treatment modalities. Here we demonstrate that the cytotoxic effect of the protein kinase C (PKC)-inhibitor N-benzoylated staurosporine (PKC412) is mediated via the PI3K/Akt pathway. Dose-dependent down-regulation of the proliferative activity, activation of the apoptotic machinery, and cell killing by PKC412 (0-1 microM) in Rat1a-fibroblasts and H-ras-oncogene-transformed fibroblasts correlated with a decrease of Akt phosphorylation and a reduced phosphorylation of the endogenous Akt-substrate GSK3-alpha. Expression of the dominant-active myristoylated form of Akt abrogated this cytotoxic effect of PKC412. Experiments with Apaf-1-deficient cells revealed that PKC412-induced cytotoxicity depends on an intact apoptosome but that the decrease of Akt phosphorylation is not attributable to apoptosis execution. Comparative experiments indicate that PKC412 and the parent-compound staurosporine down-regulate this survival pathway upstream or at the level of Akt but by a different mechanism than the PI3K-inhibitor LY294002. Furthermore, inhibition of this pathway by PKC412 is relevant for sensitization to ionizing radiation. These results demonstrate the specific role of this signaling pathway for the PKC412-mediated down-regulation of an apoptotic threshold and its cytotoxicity.

PKC412--a protein kinase inhibitor with a broad therapeutic potential.[Pubmed:10888033]

Anticancer Drug Des. 2000 Feb;15(1):17-28.

The staurosporine derivative PKC412 was originally identified as an inhibitor of protein kinase C (PKC) and subsequently shown to inhibit other kinases including the kinase insert domain receptor (KDR) (vascular endothelial growth factor receptor, VEGF-R2), the receptor of platelet-derived growth factor, and the receptor for the stem cell factor, c-kit. PKC412 showed a broad antiproliferative activity against various tumor and normal cell lines in vitro, and was able to reverse the Pgp-mediated multidrug resistance of tumor cells in vitro. Exposure of cells to PKC412 resulted in a dose-dependent increase in the G2/M phase of the cell cycle concomitant with increased polyploidy, apoptosis and enhanced sensitivity to ionizing radiation. PKC412 displayed a potent antitumor activity as single agent and was able to potentiate the antitumor activity of some of the clinically used cytotoxins (Taxol and doxorubicin) in vivo. The combined treatment of PKC412 with loco-regional ionizing irradiation showed significant antitumor activity against tumors which are resistant to both ionizing radiation and chemotherapeutic agents (dysfunctional p53). The finding that PKC412 is an inhibitor of the VEGF-mediated cellular signaling via inhibition of KDR and PKC in vitro is consistent with the in vivo inhibition of VEGF-dependent angiogenesis in a growth factor implant model. Orally administered PKC412 also strongly inhibited retinal neovascularization as well as laser-induced choroidal neovascularization in murine models. In summary, PKC412 may suppress tumor growth by inhibiting tumor angiogenesis in addition to directly-inhibiting tumor cell proliferation via its effects on PKC and/or other protein kinases. PKC412 is currently in Phase I clinical trials for treatment of advanced cancer as well as for the treatment of ischemic retinopathy.

Midostaurin (PKC412; CGP 41251) is a multi-targeted protein kinase inhibitor which inhibits PKCα/β/γ, Syk, Flk-1, Akt, PKA, c-Kit, c-Fgr, c-Src, FLT3, PDFRβ and VEGFR1/2 with IC50 ranging from 22-500 nM.

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