A phase I pharmacokinetic and safety analysis of epothilone folate (BMS-753493), a folate receptor targeted chemotherapeutic agent in humans with advanced solid tumors

Background The folate receptor alpha is selectively over-expressed in a number of human cancers. BMS-753493 is a folate conjugate of the epothilone analog BMS-748285 that was designed to selectively target folate receptor expressing cancer cells. Methods BMS-753493 was investigated in two parallel multi-institutional first-in-human phase I/IIa studies in patients with advanced solid tumors. In Study 1, patients were treated on a schedule of once daily dosing of BMS-753493 administered on Days 1, 4, 8 and 11 every 21 days with a starting dose of 5 mg daily and in Study 2, patients were treated once daily on Days 1-4 every 21 days, with a starting dose of 2.5 mg daily. Results A total of 65 patients were treated across the two studies. The maximum tolerated dose (MTD) was 26 mg in Study 1 and 15 mg in Study 2. Fatigue, transaminitis, gastrointestinal toxicity, and mucositis were dose-limiting toxicities. One patient in Study 2 developed Stevens-Johnson syndrome attributed to BMS-753493. Plasma exposures of both the conjugated and free epothilone increased in a dose related fashion in both studies and the half-life of the conjugated epothilone was 0.2-0.6 h across dose levels. No objective tumor responses were seen in either study. Conclusions BMS-753493 was generally tolerable and toxicities known to be associated with epothilone class of anticancer agents were common, although peripheral neuropathy and neutropenia appear to have been less frequent and less severe as compared to epothilones. Antitumor activity was not demonstrated and further development of BMS-753493 has been discontinued.

A phase II study of AMN107, a novel tyrosine kinase inhibitor, administered to patients (pts) with systemic mastocytosis (SM)

6588

Background: SM is a clonal hematologic disorder associated with a constitutive activation of c-kit based on point mutations of this tyrosine kinase and is characterized by mast cell infiltration of extracutaneous organs. AMN107 is a novel aminopyrimidine which potently inhibits Bcr-Abl, as well as the PDGFR and c-kit kinases. Methods: This phase II, open-label study was designed to evaluate the safety and efficacy of AMN107 (400 mg bid). SM pts meeting specific disease criteria and with a clinical indication for treatment were enrolled. Preliminary data are presented for the first 23 pts accrued prior to September 1, 2005. Results: The median age was 49 (range 33–78) yrs and the median time from diagnosis of SM was 27 (range 1 to 292) months. For those with data available, 13/17 pts had a c-kit D816V mutation in bone marrow cells. The median exposure to AMN107 was 144 days. Treatment is ongoing for 18 (78%) pts; 5 (22%) discontinued, 3 (13%) for adverse events and 2 (9%) withdrew consent. Three (13%) responses were reported (2 incomplete remissions and 1 minor response), based on serum tryptase, bone marrow mast cell infiltration and improvement of clinical symptoms. Baseline mutation data are available for 2 of the 3 responding pts and revealed the c-kit D816V mutation. Anemia was reported in 2 (9%) pts. Non-hematologic toxicities in ≥10% of pts were headache in 12 (52%) pts (Gr 3/4 in 2; 9%), fatigue in 9 (39%) pts (Gr 3/4 in 1; 4%), nausea in 8 (35%) pts, vomiting in 7 (30%) pts, pruritus in 7 (30%) pts (Gr 3/4 in 2; 9%), muscle spasms in 6 (26%) pts (Gr 3/4 in 1; 4%), diarrhea in 5 (22%) pts (Gr 3/4 in 1; 4%), upper abdominal pain, rash in 5 (22%) pts each, dizziness, pain in extremities in 4 (17%) pts each (Gr 3/4 in 1; 4% each), dyspnea, myalgia, in 4 (17%) pts each, increased ALAT in 4 (17%) pts (Gr 3/4 in 2; 9%), bone pain, abdominal pain, cough, hard feces, pustular rash in 3 (13%) pts each, and hypotension in 3 (13%) pts (Gr 3/4 in 2; 9%). There were no deaths. Conclusions: These data suggest that AMN107 has clinical activity and an acceptable safety and tolerability profile in pts with SM.

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Bcr-Abl mutations in imatinib-resistant CML and Ph+ALL patients (pts) enrolled in a phase I study of AMN107

6527

Background: AMN107 is a potent, highly selective, aminopyrimidine inhibitor which in vitro is 30-fold more potent than imatinib and active against 32/33 imatinib resistant Bcr-Abl mutations. Methods: The spectrum of mutations in Bcr-Abl was evaluated by direct sequencing of the kinase domain and surrounding regions on samples from pts with imatinib-resistant Ph+ CML or ALL in a phase I study of AMN107 (total daily dose range 50 to 1200 mg administered qd or bid). The template was created by semi-nested PCR using primers in the BCR and ABL regions of the gene. Mutations were correlated with clinical response. Results: Among 119 pts, 86 had both pre and post tx analyses: 39 (45%) had mutations at baseline, of whom 27 (69%) responded. 47 (55%) had no mutation at baseline, of whom 34 (72%) responded. The most common baseline mutations were G250E, E255K/V, E355G, F317L, H396R and M351T. New mutations were found during median follow-up of 112 (6 - 350) days in 37 pts (26 without baseline mutations). New mutations most commonly included F349V, E255K/V, E355G, G250E, M244V and T315I. Of the 37 pts, 30 had evaluations after mutations emerged, and 15 continued to respond for median of 160 (41–351) days. Fourteen mutations not previously reported occurred, 6 at codons with known imatinib resistance mutations resulting in novel amino acid substitutions. Novel mutations in multiple pts and/or multiple timepoints included E344G, F311I, E453K, E459Q and L248L. The T315I mutation was present at baseline in 1 pt who failed to respond and emerged in 4 pts, of whom follow-up was available for 3. Two continued to respond ≥ 80 days after developing the mutation and one progressed when the mutation emerged. Conclusions: AMN107 has clinical activity in pts with Ph+CML/ALL with nonmutated and mutated Bcr-Abl. At AMN107 doses used in this phase I study, new mutations often emerged, but were not a reliable predictor of clinical relapse.

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A phase II study of AMN107, a novel inhibitor of Bcr-Abl, administered to imatinib-resistant or intolerant patients (pts) with Ph+ chronic myelogenous leukemia (CML) in blast crisis (BC) or relapsed/refractory Ph+ acute lymphoblastic leukemia (ALL)

6536

Background: AMN107 is a highly selective, aminopyrimidine which is 30-fold more potent in vitro than imatinib and active against 32/33 imatinib resistant Bcr-Abl mutations. Methods: This open-label study evaluated safety and efficacy of AMN107 (400 mg bid) by hematologic/cytogenetic response (HR/CyR) rates in imatinib resistant/ intolerant BC or relapsed/refractory ALL pts. Results: Preliminary data from this ongoing study are presented for 18 BC and 6 ALL (5 relapsed/refractory, 1 minimal residual disease) pts. Baseline mutation data are available for 6 BC and 2 ALL pts: 2 and 1, respectively, had Bcr-Abl mutations. The overall median age was 54 yrs and the overall median exposure was 84 days. Seven patients remain on treatment (5 BC, 2 ALL) and 17 discontinued (3 adverse events, 9 progressive disease (PD), 3 deaths, 2 other). Two BC pts died of PD. 1 ALL pt had sudden cardiac death. HR was reported in 7 (38%) BC pts; 5 complete HR and 2 marrow responses/no evidence of leukemia. 3 BC pts had CyR (2 complete, 1 minor). Complete remission was reported in 2 (33%) ALL (1 relapsed/refractory and 1 MRD) pts. Adverse events in ≥ 10% were rash in 9 (37%) pts, thrombocytopenia in 8 (33%) pts (Gr 3/4 in 7 (29%), nausea in 7 (29%) pts, pyrexia in 7 (29%) pts (Gr 3/4 in 2 (8%)); vomiting in 7 (29%) pts (Gr 3/4 in 1 (4%), diarrhea, fatigue in 6 (25%) pts each, headache in 6 (25%) pts (Gr 3/4 in 1 (4%)), neutropenia in 6 (25%) pts (all Gr 3/4), anemia in 5 (21%) pts (Gr 3/4 in 4 (17%)), pain in extremity in 5 (21%) pts (Gr 3/4 in 1 (4%)), pain, peripheral edema in 4 (17%) pts each, pruritus in 4 (17%) pts (Gr 3/4 in 1 (4%)), leukocytosis in 3 (13%) pts (Gr 3/4 in 1 (4%)), arthralgia, pharyngolaryngeal pain, and upper abdominal pain 3 (13%) each. Conclusions: AMN107 has clinical activity and an acceptable safety and tolerability profile in pts with imatinib-resistant or intolerant BC and relapsed/refractory Ph+ ALL pts

[Table: see text]

A phase II study of AMN107, a novel inhibitor of Bcr-Abl, administered to imatinib-resistant or intolerant patients (pts) with chronic myelogenous leukemia (CML) in accelerated phase (AP)

6531

Background: AMN107 is a potent, highly selective, aminopyrimidine inhibitor which in vitro is 30-fold more potent than imatinib and is active against 32/33 imatinib resistant Bcr-Abl mutations. Methods: This open-label study was designed to evaluate the safety and efficacy of AMN107 (400 mg bid) defined by hematologic/cytogenetic response (HR/CyR) rates in imatinib resistant or intolerant AP pts. Results: Preliminary data are presented for 22 pts (77% resistant and 23% intolerant to imatinib. Treatment is ongoing for 16 (73%) pts. Median age was 62 (43–76) yrs. Median duration of AMN107 exposure was 124 (3–207) days. Median time from AP diagnosis was 6 (0.2–56) mos. Three of 5 patients with data available had a Bcr-Abl mutation at baseline. HR occurred in 14 (64%) pts of which 10 (45%) were complete, 3 (14%) were marrow responses/no evidence of leukemia, and 1 return to chronic phase. CyR occurred in 6 pts (1 each complete, partial minor, and 3 minimal). All AE’s occurring in ≥10% pts were thrombocytopenia (8 [36%] pts; Gr 3/4, 6 [27%] pts), fatigue (7 [32%]), anemia, (6 [27%]; Gr 3/4, 4 [18%] pts) pruritus, muscle spasms (6 [27%] pts each), bone pain, cough, (5 pts [23%] each) rash (5 [23%] pts; Gr 3/4, 1 [5%] pt), neutropenia (4 [18%] pts, all Gr 3/4), diarrhea, headache, myalgia, pyrexia (4 [18%] pts each), abdominal pain, chills, constipation, dyspnea, nausea, extremity pain, and peripheral edema (3 [14%] pts each). Two 2 deaths occurred, 1 pt with thrombocytopenia had a CNS bleed and 1 pt had disease progression. Conclusions: These data suggest AMN107 is clinically active and has an acceptable safety profile when administered to pts with CML-AP.

[Table: see text]

A phase II study of AMN107, a novel inhibitor of Bcr-Abl, administered to imatinib resistant and intolerant patients (pts) with chronic myelogenous leukemia (CML) in chronic phase (CP)

6534

Background: AMN107 is a potent, highly selective, aminopyrimidine inhibitor which in vitro is 30-fold more potent than imatinib and active against 32/33 imatinib resistant Bcr-Abl mutations. Methods: This open-label study was designed to evaluate the safety and efficacy of AMN107 (400 mg bid) defined by hematologic/cytogenetic response (HR/CyR) rates in imatinib resistant or intolerant CP pts. Results: For this study which remains open to enrollment, preliminary data are reported for 67 pts including 39 (58%) with imatinib-resistant and 27 (40%) imatinib-intolerant CML (1 pt unknown). The median age was 62 (range 31–80) yrs and the median time from first diagnosis to treatment was 52 (range 5–279) mos. BCR-ABL mutations associated with imatinib resistance were detected in 11/17 (65%) pts at baseline. The median duration of AMN107 exposure was 129 (range 3–225) days. Treatment is ongoing for 50 (75%) pts with 17 (25%) pts discontinued (9 adverse events, 2 disease progression, 6 other). Major CyR was observed in 13 (19%) pts (6 complete, 7 partial), minor CyR was observed in 4 (17%) pts, and minimal CyR in 5 (7%) pts. Complete HR was reported in 35 of 42 (83%) pts without a baseline CHR. AE’s in ≥ 10% of pts were headache in 24 (36%) pts, fatigue in 21 (31%) pts (Gr 3/4 in 2 (3%)), pruritus in 19 (28.4%) pts (Gr 3/4 in 1 (2%)), rash in 18 (27%) pts (Gr 3/4 in 2 (3%)), nausea in 18 (27%) pts, diarrhea in 18 (27%) pts (Gr 3/4 in 1 (2%)), constipation in 11 (16%) pts, vomiting in 10 (15%) pts, thrombocytopenia in 10 (15%) pts (Gr 3/4 in 9 (13%)), anemia in 10 (14.9%) pts (Gr 3/4, 1 (2%)), neutropenia in 9 (13%) pts (Gr 3/4 in 8 (12%)), bone pain, muscle spasms, arthralgia, peripheral edema in 8 (12%) pts each, abdominal pain and myalgia in 7 (10%) pts each (Gr 3/4 in 1 (2%) each), and dyspnea in 7 (10%) pts. No deaths occurred. Conclusions: AMN107 has clinical activity and an acceptable safety and tolerability in pts with imatinib-resistant or intolerant CML-CP.

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Reduced cardiotoxicity and comparable efficacy in a phase IIItrial of pegylated liposomal doxorubicin HCl(CAELYX™/Doxil®) versus conventional doxorubicin forfirst-line treatment of metastatic breast cancer

BACKGROUND

This study was designed to demonstrate that efficacy [progression-free survival (PFS)] of CAELYX [pegylated liposomal doxorubicin HCl (PLD)] is non-inferior to doxorubicin with significantly less cardiotoxicity in first-line treatment of women with metastatic breast cancer (MBC).

PATIENTS AND METHODS

Women (n=509) with MBC and normal cardiac function were randomized to receive either PLD 50 mg/m2 (every 4 weeks) or doxorubicin 60 mg/m2 (every 3 weeks). Cardiac event rates were based on reductions in left ventricular ejection fraction as a function of cumulative anthracycline dose.

RESULTS

PLD and doxorubicin were comparable with respect to PFS [6.9 versus 7.8 months, respectively; hazard ratio (HR)=1.00; 95% confidence interval (CI) 0.82-1.22]. Subgroup results were consistent. Overall risk of cardiotoxicity was significantly higher with doxorubicin than PLD (HR=3.16; 95%CI 1.58-6.31; P<0.001). Overall survival was similar (21 and 22 months for PLD and doxorubicin, respectively; HR=0.94; 95%CI 0.74-1.19). Alopecia (overall, 66% versus 20%; pronounced, 54% versus 7%), nausea (53% versus 37%), vomiting (31% versus 19%) and neutropenia (10% versus 4%) were more often associated with doxorubicin than PLD. Palmar-plantar erythrodysesthesia (48% versus 2%), stomatitis (22% versus 15%) and mucositis (23% versus 13%) were more often associated with PLD than doxorubicin.

CONCLUSIONS

In first-line therapy for MBC, PLD provides comparable efficacy to doxorubicin, with significantly reduced cardiotoxicity, myelosuppression, vomiting and alopecia.

Gene-target recognition among members of the myc superfamily and implications for oncogenesis

Myc and Mad family proteins regulate multiple biological processes through their capacity to influence gene expression directly. Here we show that the basic regions of Myc and Mad proteins are not functionally equivalent in oncogenesis, have separable E-box-binding activities and engage both common and distinct gene targets. Our data support the view that the opposing biological actions of Myc and Mxi1 extend beyond reciprocal regulation of common gene targets. Identification of differentially regulated gene targets provides a framework for understanding the mechanism through which the Myc superfamily governs the growth, proliferation and survival of normal and neoplastic cells.

Histone deacetylase associated with mSin3A mediates repression by the acute promyelocytic leukemia-associated PLZF protein

The PLZF gene was identified first by its fusion with the retinoic acid receptor alpha gene in the t(11;17) translocation associated with a retinoic acid resistant form of acute promyelocytic leukemia (APL). It encodes a krüppel-like zinc finger protein with a POZ domain shared with a subset of regulatory proteins including the BCL6 leukemogenic protein. PLZF, like BCL6, strongly represses transcription initiated from different promoters. Here we show that PLZF associates in vitro and in vivo with the Mad co-repressor mSin3A and the histone deacetylase HDAC1. Two domains in PLZF and the PAH1 structure of mSin3A mediate these interactions. Trichostatin A, a specific inhibitor of histone deacetylases, significantly reduces PLZF repression. These data strongly suggest that, like nuclear receptors and Mad, PLZF represses transcription by recruiting a histone deacetylase through the SMRT-mSin3-HDAC co-repressor complex. We also show that BCL6 associates with HDAC1 indicating that this type of regulation might be common to POZ/Zinc finger proteins involved in human leukemias. This work supports a role for deregulated histone deacetylation in the development of both lymphoid and myeloid neoplasia in human and suggests that targeted histone deacetylase inhibitors may be useful for treatment of certain types of malignancies.

The Ink4a tumor suppressor gene product, p19Arf, interacts with MDM2 and neutralizes MDM2's inhibition of p53

The INK4a gene encodes two distinct growth inhibitors--the cyclin-dependent kinase inhibitor p16Ink4a, which is a component of the Rb pathway, and the tumor suppressor p19Arf, which has been functionally linked to p53. Here we show that p19Arf potently suppresses oncogenic transformation in primary cells and that this function is abrogated when p53 is neutralized by viral oncoproteins and dominant-negative mutants but not by the p53 antagonist MDM2. This finding, coupled with the observations that p19Arf and MDM2 physically interact and that p19Rrf blocks MDM2-induced p53 degradation and transactivational silencing, suggests that p19Arf functions mechanistically to prevent MDM2's neutralization of p53. Together, our findings ascribe INK4a's potent tumor suppressor activity to the cooperative actions of its two protein products and their relation to the two central growth control pathways, Rb and p53.

Role for N-CoR and histone deacetylase in Sin3-mediated transcriptional repression

Normal mammalian growth and development are highly dependent on the regulation of the expression and activity of the Myc family of transcription factors. Mxi1-mediated inhibition of Myc activities requires interaction with mammalian Sin3A or Sin3B proteins, which have been purported to act as scaffolds for additional co-repressor factors. The identification of two such Sin3-associated factors, the nuclear receptor co-repressor (N-CoR) and histone deacetylase (HD1), provides a basis for Mxi1/Sin3-induced transcriptional repression and tumour suppression.

Mouse Sin3A interacts with and can functionally substitute for the amino-terminal repression of the Myc antagonist Mxi1

Mxi1 is a basic region helix-loop-helix leucine zipper (bHLH/LZ) protein that, in association with Max, antagonizes Myc oncogenic activities. A possible mechanistic basis for Mxi1-mediated repression was provided by the recent demonstration that the repressive potential of Mxi1 correlates with its ability to physically associate with mSin3B, one of two mammalian homologues of the yeast transcriptional repressor SIN3. Here, we sought to characterize more fully the physical properties of the second homologue, mSin3A and to determine whether the recruitment of mSin3A by Mxi1 is indeed required for anti-Myc activity. Transient transfection of mammalian cells showed that the mSin3A protein can associate with the strong repressive isoform of Mxi1 (Mxi1-SR) and that, like other Myc superfamily members, both mSin3A and Mxi1-SR localize to the nucleus. From a developmental standpoint, a comparative analysis of Myc, Mxi1-SR and Sin3A expression during postnatal mouse development and in differentiating mouse erythroleukemia (MEL) cells revealed that dramatic and reciprocal changes in Myc and Mxi1-SR mRNA levels are accompanied by minimal stage-specific changes in mSin3A gene expression. This constant expression profile, coupled with the observation that over-expression of mSin3A does not augment the anti-Myc activity of Mxi1-SR in the rat embryo fibroblast (REF) transformation assay, suggests that mSin3A is not a limiting factor in the regulation of Myc superfamily function. Finally, a mSin3A-Mxi1 fusion protein, in which the amino terminal mSin3-interacting domain of Mxi1-SR was replaced with the full-length mSin3A, exhibited a level of repression activity equivalent to, or greater than, the level of repression obtained with Mxi1-SR. Taken together, these observations directly demonstrate that the amino-terminal repression domain of Mxi1-SR functions solely to recruit mSin3A and possibly other proteins like mSin3A and this association is necessary for the anti-Myc activity of Mxi1-SR.

Dual myristylation and palmitylation of Src family member p59fyn affects subcellular localization

The Src family consists of nine related tyrosine protein kinases with a common domain structure, including a myristylated N-terminal glycine residue. In this report, we identify cysteine residues within the N-terminal region of the Src family member Fyn which serve as sites for palmitylation. To facilitate detection of protein fatty acylation, p59fyn was overexpressed in COS cells and incubated with radioiodinated fatty acid analogs of myristate (IC13) or palmitate (IC16). Incorporation of both fatty acids into p59fyn was readily observed. Acylation with the palmitate analog was prevented when Gly-2 was mutated to alanine, implying that N-myristylation is required for palmitylation, and when either Cys-3 or Cys-6 was mutated to serine. Palmitylation was shown to alter the distribution of p59fyn between membrane-bound and soluble fractions. In contrast, no incorporation of the palmitate analog into pp60v-src, which lacks N-terminal cysteine residues, was observed. Mutation of Ser-3 of Src to cysteine, but not Ser-6, resulted in incorporation of the palmitate analog. These results serve to delineate sequence elements important for dual acylation of proteins, and further illustrate the utility of radioiodinated fatty acid analogs for studies of protein fatty acid acylation.