Zariana Nikolova

Long-Term Results From a Randomized Phase II Trial of Standard- Versus Higher-Dose Imatinib Mesylate for Patients With Unresectable or Metastatic Gastrointestinal Stromal Tumors Expressing KIT

PURPOSE The outcome of patients diagnosed with advanced gastrointestinal stromal tumor (GIST) and treated long-term with imatinib mesylate is unknown. A previous report of a randomized phase II trial of imatinib mesylate in patients with incurable GIST detailed high response rates at both the 400 and the 600 mg/d dose levels. We conducted a long-term analysis of patients treated on the trial, including patients followed during an extension phase, to evaluate survival, patterns of failure, and potential prognostic factors, including tumor mutational status. PATIENTS AND METHODS Patients with advanced GIST were enrolled onto an open-label, multicenter trial and were randomly assigned (1:1) to receive imatinib 400 versus 600 mg/d. Data were prospectively collected on KIT mutational status, total tumor area, and other potential prognostic factors. Patients were followed for a median of 63 months. RESULTS One hundred forty-seven patients were enrolled: 73 were in arm A (imatinib 400 mg/d), and 74 were in arm B (imatinib 600 mg/d). Response rates, median progression-free survival, and median overall survival were essentially identical on both arms, and median survival was 57 months for all patients. Forty-one patients overall (28%) remained on the drug long-term. Female sex, the presence of an exon 11 mutation, and normal albumin and neutrophil levels were independently associated with better survival. CONCLUSION Nearly 50% of patients with advanced GIST who were treated with imatinib mesylate survived for more than 5 years, regardless of a 400 or 600 mg/d starting dose.

Molecular and Clinical Analysis of Locally Advanced Dermatofibrosarcoma Protuberans Treated With Imatinib: Imatinib Target Exploration Consortium Study B2225

PURPOSE The cutaneous malignant tumor dermatofibrosarcoma protuberans (DFSP) is typically associated with a translocation between chromosomes 17 and 22 that places the platelet-derived growth factor-B (PDGFB) under the control of the collagen 1A1 promoter. The purpose of this study was to evaluate molecular, cytogenetic, and kinase activation profiles in a series of DFSPs and to determine whether these biologic parameters are correlated with the clinical responses of DFSP to imatinib. PATIENTS AND METHODS We analyzed the objective radiologic and clinical response to imatinib at 400 mg twice daily in eight patients with locally advanced DFSP and two patients with metastatic disease. RESULTS Each of eight patients with locally advanced DFSP had evidence of t(17;22) and showed a clinical response to imatinib. Four of these patients had complete clinical responses. The two patients with metastatic disease had fibrosarcomatous histology and karyotypes that were substantially more complex than those typically associated with localized DFSP. One patient with metastatic DFSP and an associated t(17;22) had a partial response to imatinib but experienced disease progression after 7 months of therapy. In contrast, the other patient with metastatic disease had a tumor lacking t(17;22), and there was no clinical response to imatinib. Unexpectedly, there was minimal platelet-derived growth factor receptor-beta phosphorylation in the untreated DFSP, despite the documented presence of a PDGFB autocrine mechanism. CONCLUSION Imatinib has clinical activity against both localized and metastatic DFSP with t(17;22). However, fibrosarcomatous variants of DFSP lacking t(17;22) may not respond to imatinib.

Clinical and Molecular Studies of the Effect of Imatinib on Advanced Aggressive Fibromatosis (desmoid tumor)

PURPOSE To determine the clinical efficacy of imatinib in patients with advanced aggressive fibromatosis (AF) and to identify the molecular basis of response/nonresponse to this agent. PATIENTS AND METHODS Nineteen patients with AF were treated with imatinib (800 mg/d) as part of a phase II clinical study. Tumor specimens were analyzed for mutations of KIT, PDGFRA, PDGFRB, and CTNNB1 (beta-catenin). Tumor expression of total and activated KIT, PDGFRA, and PDGFRB were assessed using immunohistochemistry and immunoblotting techniques. We also measured plasma levels of PDGF-AA and PDGF-BB in patients and normal patient controls. RESULTS Three of 19 patients (15.7%) had a partial response to treatment, with four additional patients having stable disease that lasted more than 1 year (overall 1 year tumor control rate of 36.8%). No mutations of KIT, PDGFRA, or PDGFRB were found. Sixteen of 19 patients (84%) had mutations involving the WNT pathway (APC or CTNNB1). However, there was no correlation between WNT pathway mutations and clinical response to imatinib. AF tumors expressed minimal to null levels of KIT and PDGFRA but expressed levels of PDGFRB that are comparable with normal fibroblasts. However, PDGFRB phosphorylation was not detected, suggesting that PDGFRB is only weakly activated. AF patients had elevated levels of PDGF-AA and PDGF-BB compared with normal patient controls. Notably, the plasma level of PDGF-BB was inversely correlated with time to treatment failure. CONCLUSION Imatinib is an active agent in the treatment of advanced AF. Imatinib response in AF patients may be mediated by inhibition of PDGFRB kinase activity.

Imatinib Plasma Levels Are Correlated With Clinical Benefit in Patients With Unresectable/Metastatic Gastrointestinal Stromal Tumors

PURPOSE To study the pharmacokinetics (PK) of imatinib (IM) in patients with advanced GI stromal tumors (GISTs) treated in a randomized phase II study and to explore the potential relationship between IM plasma levels and long-term clinical outcomes. PATIENTS AND METHODS Patients were randomly assigned to receive IM at 400 mg versus 600 mg daily. IM plasma levels were analyzed in a subset of patients (n = 73) for whom PK data on day 1 and at steady-state (SS, day 29) were available. IM PK was evaluated using a population PK approach. The relationship between IM plasma exposure and clinical outcome was explored by grouping patients into quartiles according to IM trough concentration (C(min)). The clinical outcome parameters evaluated include overall objective benefit rate (OOBR; complete response plus partial response plus stable disease) time to progression (TTP), and KIT genotyping. Results IM PK exposure showed a high inter-patient variability, and clinical outcomes were correlated with IM trough levels at SS. The median TTP was 11.3 months for patients in the lowest C(min) quartile (Q1, < 1,110 ng/mL) compared with more than 30 months for Q2 to Q4 (P = .0029). OOBR was also inferior in Q1 patients. In patients with GIST with KIT exon 11 mutations (n = 39), the OOBR was 67% for Q1 patients versus 100% for all others (P = .001). CONCLUSION In patients with advanced GIST, IM trough levels at SS were associated with clinical benefit. Patients with IM C(min) below 1,100 ng/mL showed a shorter TTP and lower rate of clinical benefit (OOBR). Further studies are justified to test whether monitoring IM plasma levels might optimize clinical outcomes for patients with GIST.

Phase II, Open-Label Study Evaluating the Activity of Imatinib in Treating Life-Threatening Malignancies Known to Be Associated with Imatinib-Sensitive Tyrosine Kinases

Purpose: To evaluate the activity of imatinib in treating advanced, life-threatening malignancies expressing one or more imatinib-sensitive tyrosine kinases. Experimental Design: This was a phase II, open-label, single arm study. Patients ≥15 years old with malignancies showing histologic or molecular evidence of expression/activation of imatinib-sensitive tyrosine kinases were enrolled. Patients were treated with 400 or 800 mg/d imatinib for hematologic malignancy and solid tumors, respectively. Treatment was continued until disease progression or unacceptable toxicity. The primary objective was to identify evidence of imatinib activity with tumor response as the primary end point. Results: One hundred eighty-six patients with 40 different malignancies were enrolled (78.5% solid tumors, 21.5% hematologic malignancies). Confirmed response occurred in 8.9% of solid tumor patients (4 complete, 9 partial) and 27.5% of hematologic malignancy patients (8 complete, 3 partial). Notable activity of imatinib was observed in only five tumor types (aggressive fibromatosis, dermatofibrosarcoma protuberans, hypereosinophilic syndrome, myeloproliferative disorders, and systemic mastocytosis). A total of 106 tumors were screened for activating mutations: five KIT mutations and no platelet-derived growth factor receptor mutations were found. One patient with systemic mastocytosis and a partial response to therapy had a novel imatinib-sensitive KIT mutation (D816T). There was no clear relationship between expression or activation of wild-type imatinib-sensitive tyrosine kinases and clinical response. Conclusion: Clinical benefit was largely confined to diseases with known genomic mechanisms of activation of imatinib target kinases. Our results indicate an important role for molecular characterization of tumors to identify patients likely to benefit from imatinib treatment.

Influence of Enzyme-Inducing Antiepileptic Drugs on Trough Level of Imatinib in Glioblastoma Patients

Background: Imatinib mesylate is used in combination with hydroxyurea (HU) in ongoing clinical phase II studies in recurrent glioblastoma multiforme (GBM). CYP3A4 enzyme-inducing antiepileptic drugs (EIAEDs) like carbamazepine, phenytoin, and oxcarbazepine - as well as non-EIAEDs like valproic acid, levetiracetam, and lamotrigine - are frequently used in patients with GBM. Since CYP3A4 is the major isozyme involved in the metabolism of imatinib, we investigated the influence of EIAEDs on imatinib pharmacokinetics (pk). Methods: GBM patients received 600 mg imatinib p.o./o.d. in combination with 1.0 g HU p.o./o.d..together with either EIAEDs, non-EIAEDs, or no antiepileptic drug (non-AEDs) comedication. Trough plasma levels of imatinib and its active main metabolite N-desmethyl-imatinib (CGP74588) were determined biweekly in these patients, total 543 samples being collected from 224 patients (up to 6 times / patient). All three groups were compared to each other and with historical pharmacokinetic data obtained from patients with chronic myeloid leukemia (CML). Results: Mean imatinib trough levels in patients not receiving AEDs ( 1404 ng/ml, CV 64%) and on non-EIAEDs (1374 ng/ml, CV 46%) were comparable with mean imatinib trough levels of the historical control group of CML patients (1400 ng/ml, CV 50%). Mean trough levels of imatinib were reduced up to 2.9-fold (477 ng/ml, CV 70%) in patients treated with EIAEDs. Only slight, but although significant differences were observed in the mean trough level of the metabolite CGP74588 between EIAED-, non-EIAED and no-AED patients, 240 ng/ml (CV 57%) , 351 ng/ml (CV 34%) and 356 ng/ml (CV 52%), respectively. The corresponding mean level for CML patients was 300 ng/ml (CV 50%). Conclusion: Significant decreases of imatinib and CGP74588 trough levels were observed for patients receiving EIAEDs. The EIAED-induced reduction in trough imatinib levels can be avoided by switching to non-EIAEDs comedication or compensated by administering higher imatinib doses. In addition these data demonstrate that there is no significant difference in the pharmacokinetics of imatinib between patients with glioblastoma and CML.

PREVENTION OF GRAFT VESSEL DISEASE BY COMBINED FTY720/CYCLOSPORINE A TREATMENT IN A RAT CAROTID ARTERY TRANSPLANTATION MODEL

BACKGROUND Graft vessel disease (GVD) is an important problem often responsible for late graft loss. The effects of FTY720, an immunomodulator with a novel mechanism of action were investigated in combination with cyclosporine A (CsA) in a carotid artery allograft model. METHODS A segment of the carotid artery of Lewis rats was replaced by a DA allograft. Seven groups of eight rats were treated for 8 weeks with vehicle (P), CsA 0.3 (C0.3), 1 (C1) or 3 (C3) mg x kg(-1).day(-1) or a combination of CsA 1 with FTY 0.01 (C1F0.01), 0.03 (C1F0.03), and 0.1 (C1F0.1) mg x kg(-1).day(-1). Lumen area was estimated by magnetic resonance imaging, peripheral lymphocyte count and drug concentrations were determined at 1 and 8 weeks. Neointima, media, and lumen area were measured morphometrically. Intimal and adventitial infiltration of mononuclear cells, and medial smooth muscle cells number was assessed using a score. RESULTS FTY720 did not influence CsA blood concentrations. FTY720 but not CsA decreased the PLC dose dependently. Magnetic resonance imaging revealed that treatment groups have larger lumen size than group P. Histological and morphometric evaluation showed that all aspects of GVD were dose dependently suppressed by treatment and lumen narrowing was prevented. CONCLUSIONS CsA, at clinically relevant blood levels, suppressed GVD only partly. The addition of FTY720 was well tolerated and completely suppressed GVD development. In vivo lumen size did not correlate with the histologically estimated neointimal thickness.

Combined FTY720/cyclosporine treatment promotes graft survival and lowers the peripheral lymphocyte count in a murine cardiac allotransplantation model

BACKGROUND FTY720 lowers the peripheral lymphocyte count (PLC) by accelerating the migration of circulating lymphocytes to secondary lymphoid organs. We investigated the efficacy of combined FTY720+cyclosporine (CsA) treatment versus monotherapy on prolonging graft survival and on lowering the PLC. METHODS BALB/c hearts were heterotopically grafted in C3H mice. FTY720 was administered alone or in combination with CsA. PLC and body weight were determined on day 7, day 28, or the day of rejection. RESULTS Combining FTY720 with CsA prolonged, dose-dependently and significantly, the allograft survival. FTY720, but not CsA, lowered the PLC dose-dependently. The granulocyte count was not reduced in any group. FTY720 concentrations were not influenced by the CsA co-administration. CONCLUSIONS Combined FTY720 and CsA treatment was well tolerated, promoted graft survival, and suppressed the inflammatory allo-response. The PLC lowering correlated well with the antirejection effects in the two-drug regimens, suggesting that the PLC might guide FTY720 therapy at low doses.

Combined FTY720/cyclosporine A treatment promotes graft survival and lowers the peripheral lymphocyte count in DA to Lewis heart and skin transplantation models

OBJECTIVE The immunomodulator, FTY720, lowers the peripheral lymphocyte count (PLC) by inducing migration of circulating lymphocytes to secondary lymphoid organs. We investigated the efficacy of mono- vs. combined-FTY720/CsA therapy on graft survival (GS) and on lowering the PLC in a solid organ and a skin graft model, using strains with strong MHC disparity. METHODS Heterotopic cardiac or tail skin grafting was performed using the DA (RT1a) to Lewis (RT1(1)) rat strain combination. FTY720 was administered as a single daily dose by gavage alone or in combination with subcutaneously delivered CsA. PLC, body weight and drug concentrations were determined on day 7, 28, or the day of rejection. MAIN FINDINGS In placebo-treated animals the heart and skin allografts rejected after 6 and 8 days. FTY720 delayed rejection of both the solid organ and skin grafts. The maximal effect was achieved at 1 mg x kg(-l) x day(-1) FTY720, resulting in a median survival time (MST) of 14 days for both allotransplants comparable to the effect achieved by 1 mg x kg x day(-1) CsA in both models. In the cardiac graft experiment with CsA co-administration, doses of 0.3 and 1 mg/kg were used. Under these conditions very small doses of FTY720 were effective in maintaining grafts throughout the treatment period. Adding higher FTY720 doses to the 1 mg x kg(-1) x day(-1) CsA was needed to effectively extend the skin GS, e.g. 0.3 mg x kg(-l) x day(-1) FTY720 prolonged GS from 13 to 47.5 days MST, i.e. well beyond the 28 day-treatment period. CsA did not influence the PLC at clinically relevant doses. FTY720 lowered the PLC significantly and dose-dependently, at doses lower than those needed for the prolongation of both cardiac and skin GS with FTY720 monotherapy. In rats with skin grafts the PLC was markedly lowered up to 1 mg x kg(-1) x day(-1) FTY720, whereas, in the heart model, it was lowered up to 0.1 mg x kg(-1) x day(-1). Independently of the graft type, within the combination regimens 0.3 mg x kg(-1) x day(-1) FTY720 achieved a maximal PLC depletion. CONCLUSIONS Combining FTY720 and CsA was very well tolerated with respect to weight gain and lack of any clinically detectable infections. In the strain combination used FTY720 monotherapy was less effective than previously reported in maintaining grafts. The two-drug regimens extended strikingly the GS for both models. However, the prolongation of the heart GS was smoothly dose-related with FTY720 doses ranging from 0.01 to 1 mg x kg(-1) x day(-1) , whereas, the skin graft prolongation was modest at doses up to 0.1 mg x kg(-1) x day(-1) and remarkably enhanced at 0.3 and 1 mg x kg(-1) x day(-1) FTY720.

Efficacy of SDZ RAD compared with CsA monotherapy and combined RAD/FTY720 treatment in a murine cardiac allotransplantation model

OBJECTIVE The macrolide immunosuppressant RAD and the immunomodulator FTY720 have distinct mechanisms ofaction. We investigated the efficacy of RAD (everolimus, certican) alone or in combination with FTY720 on graft survival (GS)and histology in comparison with CsA, using mouse strains with strong MHC disparity. METHODS Heterotopic cardiac grafting was performed using the C57B1/6 to C3H strain combination. Osmotic mini-pumps filled with CsA or RAD were implanted subcutaneously. IFTY720 was administered as a single daily dose by gavage. Peripheral lymphocyte count (PLC) was determined at 1, 4 and 8 weeks or on the day of sacrifice. Body weight was recorded on the day of surgery and weekly. Grafts were histologically evaluated. MAIN FINDINGS In placebo-treated mice the allografts were rejected after 7 days. Monotherapy with 10 and 30 mg/kg/day CsA achieved 10 and 22.5 days median survival time (MST), while 0.1, 0.3, 1 and 3 mg/kg/day RAD resulted in 10.5, 20, > 56 and > 56 days MST, respectively. FTY720 lowered the PLC significantly, while the lower CsA dose and RAD did not influence the PLC. Adding FTY720 to the 0.6 mg/kg/day dose of RAD extended GS modestly but reduced significantly the perivascular infiltration and endothelialitis in the grafts compared with RAD monotherapy. CONCLUSIONS Underthe conditions of the present experiment RAD was more potent than CsA in extending the GS. Combining FTY720 and RADwas well tolerated with respect to weight gain and lack of clinically detectable infections in the mice. The 2-drug regimens suppressed the inflammatory allo-response better than RAD monotherapy.