Pharmacokinetic/pharmacodynamic modelling-based optimisation of administration schedule for the histone deacetylase inhibitor abexinostat (S78454/PCI-24781) in phase I

Abexinostat, an oral pan-histone deacetylase inhibitor (HDACi), was evaluated in patients with advanced solid tumours in two single agent phase I studies (PCYC-402 and CL1-78454-002). In PCYC-402 study testing four different administration schedules, the maximum tolerated dose (MTD) was established at 75 mg/m² BID (twice daily) and the recommended dose at 60 mg/m² BID regardless of the schedule tested. The dose limiting toxicity (DLT), consistently observed across all these schedules, was reversible thrombocytopenia.The CL1-78454-002 study was initially investigating an additional schedule of 14 days on/7 days off. While testing two first cohorts, thrombocytopenia was observed without reaching DLT. To address this issue, a pharmacokinetic/pharmacodynamic (PK/PD) model was used to predict the optimal schedule allowing higher doses with minimal thrombocytopenia. Several administration schedules were simulated using this model. A 4 days on/3 days off schedule was associated with the smallest platelet decrease. Accordingly, the CL1-78454-002 study was amended. After reaching MTD1 (75 mg/m² BID) with the initial schedule, subsequent cohorts received abexinostat on a revised schedule of 4 days on/3 days off, starting at one dose level below MTD1 (60 mg/m² BID). As expected, the dose-escalation continued for two more dose levels beyond MTD1. The MTD2 reached for this optimised schedule was 105 mg/m² BID and the recommended dose 90 mg/m² BID.In conclusion, early understanding of toxicities and PK determination allowed us to build a PK/PD model of thrombocytopenia, which predicted the optimal administration schedule. This optimised schedule is currently used in the trials in solid tumours with abexinostat.     

BIBW2992, an irreversible EGFR/HER2 inhibitor highly effective in preclinical lung cancer models

Genetic alterations in the kinase domain of the epidermal growth factor receptor (EGFR) in non-small cell lung cancer (NSCLC) patients are associated with sensitivity to treatment with small molecule tyrosine kinase inhibitors. Although first-generation reversible, ATP-competitive inhibitors showed encouraging clinical responses in lung adenocarcinoma tumors harboring such EGFR mutations, almost all patients developed resistance to these inhibitors over time. Such resistance to first-generation EGFR inhibitors was frequently linked to an acquired T790M point mutation in the kinase domain of EGFR, or upregulation of signaling pathways downstream of HER3. Overcoming these mechanisms of resistance, as well as primary resistance to reversible EGFR inhibitors driven by a subset of EGFR mutations, will be necessary for development of an effective targeted therapy regimen. Here, we show that BIBW2992, an anilino-quinazoline designed to irreversibly bind EGFR and HER2, potently suppresses the kinase activity of wild-type and activated EGFR and HER2 mutants, including erlotinib-resistant isoforms. Consistent with this activity, BIBW2992 suppresses transformation in isogenic cell-based assays, inhibits survival of cancer cell lines and induces tumor regression in xenograft and transgenic lung cancer models, with superior activity over erlotinib. These findings encourage further testing of BIBW2992 in lung cancer patients harboring EGFR or HER2 oncogenes.     

AG337, a novel lipophilic thymidylate synthase inhibitor: in vitro and in vivo preclinical studies

3,4-Dihydro-2-amino-6-methyl-4-oxo-5-(4-pyridylthio)-quinazoline dihydrochloride (AG337) is a water-soluble, lipophilic inhibitor of thymidylate synthase (TS) designed using X-ray structure-based methodologies to interact at the folate cofactor binding site of the enzyme. The aim of the design program was to identify TS inhibitors with different pharmacological characteristics from classical folate analogs and, most notably, to develop non-glutamate-containing molecules which would not require facilitated transport for uptake and would not undergo intracellular polyglutamylation. One molecule which resulted from this program, AG337, inhibits purified recombinant human TS with a K_i of 11 nM, and displays non-competitive inhibition kinetics. It was further shown to inhibit cell growth in a panel of cell lines of murine and human origin, displaying an IC₅₀ of between 0.39 μM and 6.6 μM. TS was suggested as the locus of action of AG337 by the ability of thymidine to antagonize cell growth inhibition and the direct demonstration of TS inhibition in whole cells using a tritium release assay. The demonstration, by flow cytometry, that AG337-treated L1210 cells were arrested in the S phase of the cell cycle was also consistent with a blockage of TS, as was the pattern of ribonucleotide and deoxyribonucleotide pool modulation in AG337-treated cells, which showed significant reduction in TTP levels. The effects of AG337 were quickly reversed on removal of the drug, suggesting, as would be expected for a lipophilic agent, that there is rapid influx and efflux from cells and no intracellular metabolism to derivatives with enhanced retention. In vivo, AG337 was highly active against the thymidine kinase-deficient murine L5178Y/TK^- lymphoma implanted either i.p. or i.m. following i.p. or oral delivery. Prolonged dosing periods of 5 or 10 days were required for activity, and efficacy was improved with twice-daily dose administration. Dose levels of 25 mg/kg delivered i.p. twice daily for 10 days, 50 mg/kg once daily for 10 days, or 100 mg/kg once daily for 5 days elicited 100% cures against the i.p. tumor. Doses required for activity against the i.m. tumor were higher (100 mg/kg i.p. twice daily for 5 or 10 days) but demonstrated the ability of AG337 to penetrate solid tissue barriers. Oral delivery required doses of ≥150 mg/kg twice daily for periods of 5–10 days to produce 100% cure rates against both i.m. and i.p. implanted tumors. These results were consistent with the pharmacokinetic parameters determined in rats, for which oral bioavailability of 30–50% was determined, together with a relatively short elimination half life of 2 h. Clinical studies with AG337 are currently in progress. Received: 10 March 1995/Accepted: 14 May 1995     

Combined targeting of EGFR-dependent and VEGF-dependent pathways: rationale, preclinical studies and clinical applications

Cellular heterogeneity, redundancy of molecular pathways and effects of the microenvironment contribute to the survival, motility and metastasis of cells in solid tumors. It is unlikely that tumors are entirely dependent on only one abnormally activated signaling pathway; consequently, treatment with an agent that interferes with a single target may be insufficient. Combined blockade of functionally linked and relevant multiple targets has become an attractive therapeutic strategy. The EGFR and ERBB2 (HER2) pathways and VEGF-dependent angiogenesis have a pivotal role in cancer pathogenesis and progression. Robust experimental evidence has shown that these pathways are functionally linked and has demonstrated a suggested role for VEGF in the acquired resistance to anti-ERBB drugs when these receptors are pharmacologically blocked. Combined inhibition of ERBB and VEGF signaling interferes with a molecular feedback loop responsible for acquired resistance to anti-ERBB agents and promotes apoptosis while ablating tumor-induced angiogenesis. To this aim, either two agents highly selective against VEGF and ERBB respectively, or, alternatively, a single multitargeted agent, can be used. Preclinical studies have proven the efficacy of both these approaches and early clinical studies have provided encouraging results. This Review discusses the experimental rationale for, preclinical studies of and clinical trials on combined blockade of ERBB and VEGF signaling.     

Formononetin,a novel FGFR2 inhibitor,potently inhibits angiogenesis and tumor growth in preclinical models

Most anti-angiogenic therapies currently being evaluated in clinical trials target vascular endothelial growth factor (VEGF) pathway, however, the tumor vasculature can acquire resistance to VEGF-targeted therapy by shifting to other angiogenesis mechanisms. Therefore, other potential therapeutic agents that block non-VEGF angiogenic pathways need to be evaluated. Here we identified formononetin as a novel agent with potential anti-angiogenic and anti-cancer activities. Formononetin demonstrated inhibition of endothelial cell proliferation, migration, and tube formation in response to basic fibroblast growth factor 2 (FGF2). In ex vivo and in vivo angiogenesis assays, formononetin suppressed FGF2-induced microvessel sprouting of rat aortic rings and angiogenesis. To understand the underlying molecular basis, we examined the effects of formononetin on different molecular components in treated endothelial cell, and found that formononetin suppressed FGF2-triggered activation of FGFR2 and protein kinase B (Akt) signaling. Moreover, formononetin directly inhibited proliferation and blocked the oncogenic signaling pathways in breast cancer cell. In vivo, using xenograft models of breast cancer, formononetin showed growth-inhibitory activity associated with inhibition of tumor angiogenesis. Moreover, formononetin enhanced the effect of VEGFR2 inhibitor sunitinib on tumor growth inhibition. Taken together, our results indicate that formononetin targets the FGFR2-mediated Akt signaling pathway, leading to the suppression of tumor growth and angiogenesis.     

Phase I clinical, pharmacokinetic and pharmacodynamic study of SB939, an oral histone deacetylase (HDAC) inhibitor, in patients with advanced solid tumours

Background:

SB939 is an orally available, competitive histone deacetylase (HDAC) inhibitor selective for class I, II and IV histone deacetylases. Preclinical evaluation of SB939 revealed a profile suggesting improved efficacy compared to other HDAC inhibitors. This phase I study was carried out to determine the safety, dose-limiting toxicity, recommended phase II dose (RPTD), as well as pharmacokinetic (PK) and pharmacodynamic (PD) profiles of SB939 in a daily × 5 schedule in advanced solid tumours.

Methods:

Sequential dose-escalating cohorts of patients were enrolled into 8 dose levels. At dose level 1, SB939 was taken on days 1–3 and 15–17 every 4 weeks, then on days 1–5 and 15–19 for other dose levels. Detailed PK sampling was performed in cycle 1, days 1 and 5. Peripheral blood mononuclear cells (PBMCs) were collected on cycle 1 at various time points for determination of acetylated histone H3 (AcH3) levels.

Results:

In total, 38 patients received a total of 96 cycles of treatment. The maximal administered dose was 90 mg and the RPTD was 60 mg given 5 consecutive days every 2 weeks. The most frequent non-hematologic adverse events (AEs) of at least possible attribution to SB939 were fatigue, nausea, vomiting, anorexia and diarrhoea. Pharmacokinetic analysis showed dose-proportional increases in AUC across the doses evaluated. Elimination half-life was 5.6–8.9 h. There was no clear relationship between AcH3 changes and dose level or anti-tumour response.

Conclusions:

SB939 is well tolerated in patients with advanced solid tumours. The RPTD of this drug is 60 mg on a schedule of 5 consecutive days every 2 weeks. The toxicities of SB939 are consistent with other HDAC inhibitors.     

Phosphatase inhibitor, sodium stibogluconate, in combination with interferon (IFN) alpha 2b: phase I trials to identify pharmacodynamic and clinical effects

Since sodium stibogluconate (SSG) inhibited phosphatases including SHP-1 and augmented anti-tumor actions of IFN-α2b in vitro and in mice, two Phase I trials of SSG/IFN-α2b combination were undertaken to evaluate safety and target inhibition. Escalating doses of SSG (200-1200 mg/m2) and fixed doses of IFN-α2b (3x106 units/m2) with or without chemotherapy (dacarbazine, vinblastine, cisplatin) were evaluated for side effects and impact on SHP-1 phospho-substrates and IFNα-stimulated-genes (ISGs) in peripheral blood in 40 patients with metastatic melanoma, soft tissue sarcomas, gastrointestinal stromal tumors, and breast or colorectal carcinomas who did not have other established treatment options. Common adverse events were bone marrow suppression, fatigue, gastrointestinal upset, and asymptomatic lipase elevation (n=13); the latter was dose related and mostly after 10d of SSG/IFN-α2b in combination. Levels of SHP-1 substrates (pSTAT1, pSTAT3, pLck and pSlp76) were increased (up to 3x) in peripheral blood cells following SSG with no potentiation by combination with IFN-α2b. Representative ISGs in peripheral blood were induced after IFN-α2b at 4 and 24 hrs with selective modulations by combination. The median time on trials was 2.3 months (10-281d) with no objective regression of disease. Alive at 1y were 17/40 (43%) patients and after 2y were 8/40 (20%) following treatment initiation. These data demonstrate that SSG impacted signal molecules consistent with PTP inhibition and was tolerated in combination with IFN-α2b. Phase II investigations of SSG could safely utilize doses of up to 1200 mg/m2 of SSG for up to 10d alone or in combination with IFN-α2b with or without chemotherapy.     

The impact of pharmacokinetically guided dose escalation strategies in phase I clinical trials: critical evaluation and recommendations for future studies.

Phase I studies requiring multiple dose escalation steps have led to the development of pharmacokinetically guided dose escalation (PGDE) strategies to expedite the conduct of early clinical trials. This article critically reviews PGDE strategies for a number of new anticancer agents including amphethinile, brequinar sodium, iodo-doxorubicin, the anthrapyrazoles (DuP 941, DuP 942 and DuP 937), rhizoxin, and aphidicolin glycinate. The benefits and problems associated with PGDE are examined. Recommendations are made for the optimal deployment of pharmacological information in future phase I studies.     

A study of amsalog (CI-921) administered orally on a 5-day schedule, with bioavailability and pharmacokinetically guided dose escalation

PURPOSE: Amsalog is a derivative of 9-aminoacridine. Phase I studies using intravenous (i.v.) amsalog have shown the dose-limiting toxicity (DLT) to be phlebitis and myelosuppression. Phase II studies using a variety of schedules have shown evidence of activity in patients with large-cell lung, breast, and head and neck cancers. Preclinical studies demonstrated that amsalog is active orally: a clinical study of the oral bioavailability of amsalog was therefore performed. METHODS: A group of 20 patients with refractory malignancies were treated. There were two phases of the study: a pharmacokinetic comparison of i.v. against oral amsalog, followed by a pharmacokinetically guided oral dose escalation study. In the first phase of the study, 11 patients were treated. Amsalog 50 mg/m2 was administered i.v., and 50 mg/m2 and 200 mg/m2 orally. In the second phase of the study, 9 patients were treated in three cohorts of three. On day 1 of a 5-day schedule, amsalog was administered i.v. at the maximum tolerated dose (MTD) of 200 mg/m2. Subsequent doses were given orally, starting at a dose of 200 mg/m2 per day, with intrapatient dose escalation of up to 100% for the second cycle. Doses were escalated further in subsequent cohorts, based on oral bioavailability and toxicity. RESULTS: Oral bioavailability of 50 mg/m2 amsalog was 34%. In the dose escalation phase, DLT was neutropenia; other toxicities included malaise and nausea. The MTD was 1600 mg/m2 per day for 5 days. The plasma AUC using 1600 mg/m2 by the oral route was higher than that achieved using 200 mg/m2 by the i.v. route. CONCLUSION: Amsalog can be tolerated orally on a 5-day schedule at doses up to 1600 mg/m2. The recommended dose for further evaluation is 800 mg/m2 daily for 5 days, repeated three weekly.     

Pharmacologically directed design of the dose rate and schedule of 2',2'-difluorodeoxycytidine (Gemcitabine) administration in leukemia

The objective of this study was to determine the dose rate of 2',2'-difluorodeoxycytidine (dFdC) that maximizes the accumulation of the active 5'-triphosphate (dFdCTP) in circulating leukemia cells during therapy. The investigational approach was to evaluate the relationship between plasma dFdC and the accumulation of dFdCTP by circulating leukemia cells during infusion of different dFdC dose rates in the same individuals. Four patients with relapsed leukemia were treated weekly with two or three consecutive infusions of 800 mg/m2, the first administered over 1 h, the second over 2 h, and the third over 3 h. Two patients, one with acute myelogenous leukemia and one with acute lymphocytic leukemia, received all three infusions, but thrombocytopenia prohibited infusion of the third dose to two patients with chronic lymphocytic leukemia. The average steady-state plasma dFdC levels, achieved within 15 min after the infusion began, were 43.8 microM during infusion of 800 mg/m2/h, 9.4 microM during infusion of 400 mg/m2/h, and 5.6 microM at 267 mg/m2/h. The median area under the concentration times time curve of dFdCTP in leukemia cells during infusion was increased 2.3- and 5.1-fold for the 2- and 3-h infusions, respectively. In vitro incubations of leukemia cells from the four patients with 2.5-100 microM dFdC for 1 h showed that the maximum cellular accumulation of dFdCTP was produced by 15-20 microM dFdC. We conclude that a dose rate of greater than 400 mg/m2/h was required to achieve plasma dFdC levels that supported the maximum rate of dFdCTP accumulation in leukemia cells.     

Recent advances in the preclinical and clinical immunopharmacology of interleukin-2: emphasis on IL-2 as an immunorestorative agent

Interleukin-2 (IL-2) is a chemically defined lymphokine (LK) available as mixed human (LK) preparations, as partially purified lymphoblastoid IL-2, or as recombinant human IL-2. Each has different actions dependent on companion LKs showing synergistic interaction (e.g., IL-1 and gamma-interferon (gamma-IFN]). IL-2 acts to expand activated T cells; to activate natural killer (NK) cells, lymphokine-activated killer (LAK) cells, and cytolytic T cells (CTL); to regulate T-cell ontogeny via actions on prothymocytes and immature T cells; and to induce gamma-IFN and activate tumoricidal macrophages. IL-2 acts via specific cell surface receptors on protein kinase C and cyclic GMP-related mechanisms. While stable, its in vivo half-life is short and its persistence is important for it to induce a response. Toxicities include an influenzia-like syndrome, anemia, eosinophilia, and fluid accumulation. In vivo actions include augmentation of cytotoxic responses at high doses, T-cell adjuvant actions, and T-cell restorative actions at midrange doses and at low doses with companion LKs. Antitumor responses in man and animals occur, but irregularly. They are maximized by the concomitant use of LAK cells, cytoreductive therapy, antisuppressor cell therapy, and regional or persistent administration. IL-2 offers hope for more effective therapy of cancer and a variety of immunodeficiency diseases involving IL-2 defects, including AIDS, viral infections, and autoimmune diseases.     

A phase I dose escalation study of BIBW 2992, an irreversible dual inhibitor of epidermal growth factor receptor 1 (EGFR) and 2 (HER2) tyrosine kinase in a 2-week on, 2-week off schedule in patients with advanced solid tumours

To assess tolerability, pharmacokinetics (PK), pharmacodynamics (PD) and clinical activity of the dual epidermal growth factor receptor (EGFR) 1 and 2 (HER2) tyrosine kinase inhibitor BIBW 2992. An escalating schedule of once-daily (OD) BIBW 2992 for 14 days followed by 14 days off medication was explored. Thirty-eight patients were enrolled. Dose levels were 10, 20, 30, 45, 70, 85, and 100 mg. At 100 mg dose-limiting toxicity (DLT) (common toxicity criteria grade 3 skin rash and grade 3 diarrhoea despite treatment with loperamide) occurred in two patients. In the next-lower dose of 70 mg, DLT (grade 3 fatigue and ALAT elevation) occurred in one of six patients. An intermediate dose level of 85 mg was studied. Here DLT occurred in two patients (grade 3 diarrhoea despite treatment and grade 2 diarrhoea lasting more than 7 days despite treatment). An additional 12 patients were treated at 70 mg. BIBW 2992 PK after single and multiple doses revealed moderately fast absorption, and no deviation from dose proportionality. Pharmacodynamics analysis in skin biopsies did not show significant changes in EGFR-associated biomarkers. However, a significant inhibitory effect on the proliferation index of epidermal keratinocytes was observed. No partial or complete responses were observed, stable disease lasting more than four cycles was seen in seven patients. The recommended dose for studies with BIBW 2992 for 14 days followed by 14 days off medication is 70 mg OD.     

Repetitive weekly cycles of interleukin-2. II. Clinical and immunologic effects of dose, schedule, and addition of indomethacin

Clinical trials with high doses of interleukin 2 (IL-2) have shown antitumor responses, but many of the patients have experienced severe and occasionally life-threatening toxic effects. Preclinical studies indicate that modifications in IL-2 dose, route, and schedule can influence both immune activation and antitumor effects. This study evaluated the clinical tolerance to and immunologic modifications induced by four repetitive weekly cycles of IL-2, with two dose levels (1 X 10(6) and 3 X 10(6) U/m2 per day) of IL-2 and three different daily administration schedules [bolus, continuous, or combined (bolus and continuous)], with and without indomethacin treatment. Patients in all treatment groups experienced acceptable, non-life-threatening toxic effects and immune system stimulation characterized by rebound lymphocytosis with increased numbers of natural killer and lymphokine-activated killer cells and enhanced direct cytolytic function. These immune changes were significantly enhanced by the repetition of IL-2 cycles beyond the first week of therapy. At an IL-2 dose of 3 X 10(6) U/m2 per day, bolus IL-2 was less immunostimulatory than continuous-infusion IL-2. The combined regimen (with half of each daily dose given as a bolus and half as a 24-hr infusion) was as stimulatory as continuous-infusion IL-2 and also induced antitumor effects. Finally, the addition of indomethacin to this regimen did not significantly modify in vitro or in vivo immune response parameters but appeared to worsen the systemic toxic effects of renal dysfunction and capillary leakage. These results suggest that continuous or combined infusion of IL-2 at 3 X 10(6) U/m2 per day on this schedule should be considered for further testing in phase II trials or in combination with other therapeutic modalities.     

Early phase II study of the new aromatase inhibitor YM511 in postmenopausal patients with breast cancer. Difficulty in clinical dose recommendation based on preclinical and phase I findings

BACKGROUND: A phase II study of a non-steroidal selective aromatase inhibitor, YM511, 4-[N-bromobenzyl]-N-(4H-1,2,4-triazol-4-yl)amino) benzonitrile, was conducted to evaluate the anti-tumor response, dose-dependence of response rate and tolerability in postmenopausal patients with advanced breast cancer. PATIENTS AND METHODS: Patients were randomly allocated to a dose of 0.3, 1, 3, 10 or 30 mg after stratification according to PS, previous therapy and ER, and were administered the drug orally once a day. RESULTS: Of 98 eligible patients, 6 achieved complete response (CR) and 14 partial response (PR), resulting in an objective response rate of 20.4%. In addition, 13 patients achieved NC lasting more than 24 weeks (L-NC), resulting in an overall success rate of 33.7%. However, no clear dose-dependence of response rate was observed. Significant reduction of serum estradiol level was observed at all doses. Median time to progression of disease was 61-233 days. Toxicity was mild or moderate in severity. Fifty-five adverse events were reported in 38 patients, the most common being gastrointestinal disorders such as nausea, vomiting and anorexia (18 events) and constitutional symptoms such as asthenia, hot flushes and common cold syndrome (14 events). The frequency of drug-related adverse events was not dose-related. Abnormalities in hematological laboratory values and blood biochemistry, which were probably drug-related, were less than 5% in frequency except for cholesterol level, and were light or moderate in severity. CONCLUSION: YM511 appeared to be effective and safe in postmenopausal patients with breast cancer. Dose-dependent increase in response rate was not clearly observed at doses from 0.3 mg/day to 30 mg/day. The recommended dose of YM511 for further studies is 0.3 mg or less than 0.3 mg.