Phase II trial of N,N-diethyl-2-[4-(phenylmethyl)phenoxy]ethanamine.HCl and doxorubicin chemotherapy in metastatic breast cancer: A National Cancer Institute of Canada clinical trials group study

Factors associated with failure of oncology drugs in late-stage clinical development: A systematic review

BACKGROUND

We aimed to describe the reasons for failure of experimental anticancer drugs in late-stage clinical development.

MATERIAL AND METHODS

We searched the PharmaProjects database (https://citeline.com/products/pharmaprojects/) for anticancer drugs discontinued between 01/01/2009 and 06/30/2014. Drug programs that reached phase III trials, but never gained Food and Drug Administration (FDA) approval were compared to 37 anti-cancer drugs achieving FDA approval in this time period.

RESULTS

Forty-two drugs fit our criteria for development failures. These failed drugs (49% targeted, 23% cytotoxics, and 28% other) were tested in 43 cancer indications (drug programs). Only 16% (7/43) of failed drug programs adopted a biomarker-driven rationale for patient selection versus 57% (21/37) of successful drug programs (P<0.001). Phase II trial information was available in 32 of 43 failed drug programs and in 32 of 37 successful programs. Nine of the 32 trials (28%) of failed drugs versus 28 of 32 trials (87%) of successful drugs (P<0.001) achieved proof of concept (single agent response rate (RR) ⩾20% or combination therapy showing a ⩾20% RR increase above the median historical RR without the experimental agent (with a minimal absolute increase of 5%) or a randomized phase II trial showing significance (P⩽0.05) for its primary outcome). No pattern of study sites, trial design or funding characteristics emerged from the failed drug analysis.

CONCLUSION

For drugs that reached Phase III, lack of a biomarker-driven strategy and failure to attain proof of concept in phase II are potential risk factors for later discontinuation, especially for targeted agents.

5,6-Epoxy-cholesterols contribute to the anticancer pharmacology of tamoxifen in breast cancer cells

Tamoxifen (Tam) is a selective estrogen receptor modulator (SERM) that remains one of the major drugs used in the hormonotherapy of breast cancer (BC). In addition to its SERM activity, we recently showed that the oxidative metabolism of cholesterol plays a role in its anticancer pharmacology. We established that these effects were not regulated by the ER but by the microsomal antiestrogen binding site/cholesterol-5,6-epoxide hydrolase complex (AEBS/ChEH). The present study aimed to identify the oxysterols that are produced under Tam treatment and to define their mechanisms of action. Tam and PBPE (a selective AEBS/ChEH ligand) stimulated the production and the accumulation of 5,6α-epoxy-cholesterol (5,6α-EC), 5,6α-epoxy-cholesterol-3β-sulfate (5,6-ECS), 5,6β-epoxy-cholesterol (5,6β-EC) in MCF-7 cells through a ROS-dependent mechanism, by inhibiting ChEH and inducing sulfation of 5,6α-EC by SULT2B1b. We showed that only 5,6α-EC was responsible for the induction of triacylglycerol (TAG) biosynthesis by Tam and PBPE, through the modulation of the oxysterol receptor LXRβ. The cytotoxicity mediated by Tam and PBPE was triggered by 5,6β-EC through an LXRβ-independent route and by 5,6-ECS through an LXRβ-dependent mechanism. The importance of SULT2B1b was confirmed by its ectopic expression in the SULT2B1b(-) MDA-MB-231 cells, which became sensitive to 5,6α-EC, Tam or PBPE at a comparable level to MCF-7 cells. This study established that 5,6-EC metabolites contribute to the anticancer pharmacology of Tam and highlights a novel signaling pathway that points to a rationale for re-sensitizing BC cells to Tam and AEBS/ChEH ligands.

N,N-diethyl-2-[4-(phenylmethyl) phenoxy] ethanamine (DPPE; tesmilifene), a chemopotentiating agent with hormetic effects on DNA synthesis in vitro, may improve survival in patients with metastatic breast cancer

N,N-diethyl-2-[4-(phenylmethyl) phenoxy] ethanamine (DPPE; tesmilifene) is a novel anti-histaminic and chemopotentiating agent that has a hormetic effect on DNA synthesis in MCF (Michigan Cancer Foundation)-7 human breast cancer cells in vitro and stimulates the growth of experimental tumors in rodents. In a prospectively randomized phase three trial (NCIC MA.19), 152 patients who were co-administered DPPE and doxorubicin survived 50% longer (P < 0.03) than 153 patients who were administered the same dose and schedule of doxorubicin alone. At clinically relevant in vitro concentrations that do not inhibit the P-glycoprotein (P-gp) pump, DPPE selectively sensitizes the cancer cells that express the multiple drug resistance phenotype, making them more susceptible to the cytotoxic effects of chemotherapeutic agents, including anthracyclines and taxanes. Based on its previously demonstrated interaction with histamine at CYP3A4, a P450 that metabolizes arachidonic acid, and its induction of high levels of prostacyclin in the gut of rodents, modulation by DPPE of the intracellular concentration of arachidonate products, such as hydroxyeicosatetraeinoic acids, implicated in increased cancer cell proliferation and metastasis, is postulated.

Development of inhibitors of ATP-binding cassette drug transporters: present status and challenges

BACKGROUND

Multi-drug resistance (MDR) of cancer cells is an obstacle to effective chemotherapy of cancer. The ATP-binding cassette (ABC) transporters, including P-glycoprotein (ABCB1), MRP1 (ABCC1) and ABCG2, play an important role in the development of this resistance. An attractive approach to overcoming MDR is the inhibition of the pumping action of these transporters. Several inhibitors/modulators of ABC transporters have been developed, but cytotoxic effects and adverse pharmacokinetics have prohibited their use. The ongoing search for such inhibitors/modulators that can be applied in the clinic has led to three generations of compounds. The most recent inhibitors are more potent and less toxic than first-generation compounds, yet some are still prone to adverse effects, poor solubility and unfavorable changes in the pharmacokinetics of the anticancer drugs.

OBJECTIVE

This review provides an update of the published work on the development of potent modulators to overcome MDR in cancer cells, their present status in clinical studies and suggestions for further improvement to obtain better inhibitors.

METHODS

This review summarizes recent advances in the development of less toxic modulators, including small molecules and natural products. In addition, a brief overview of other novel approaches that can be used to inhibit ABC drug transporters mediating MDR has also been provided.

CONCLUSION

The multifactorial nature of MDR indicates that it may be important to develop modulators that can simultaneously inhibit both the function of the drug transporters and key signaling pathways, which are responsible for development of this phenomenon.

Tesmilifene may enhance breast cancer chemotherapy by killing a clone of aggressive, multi-drug resistant cells through its action on the p-glycoprotein pump

Tesmilifene is a novel potentiator of chemotherapy which, when added to doxorubicin, achieved an unexpected and very large survival advantage over doxorubicin alone in a randomized trial in advanced breast cancer. This trial was unusual in that the early endpoints (response rate and median progression-free survival) were equivalent in the two arms, despite the ultimate survival difference. These aspects, coupled with the absence of a coherent molecular mechanism of action, and a pending confirmatory trial, have led oncologists to hold judgement on this drug. This paper reacts to this in three ways: firstly, a forensic subgroup analysis is presented with an explanation as to why it strongly supports the veracity of the survival difference; secondly a novel cellular explanation is provided for the decoupling of the early and late (survival) endpoints; finally, a molecular mechanism of action is proposed, for the first time, which reconciles the peculiarities of the trial with the laboratory data and background literature. This hypothesis explains how tesmilifene could meld two of the apparent strengths of the cancer cell (drug resistance pumps, and hypoxia-adapted energetics) into a potent weapon of self-destruction. Tesmilifene is proposed to allow chemotherapy (e.g. anthracycline or taxane) to additionally kill a small but critical population (clone) of aggressive, multi-drug resistant cells, the benefits of which cannot be appreciated until a period of time (about 6-8 months) has elapsed. These cells, present in women with more rapidly relapsing disease, very likely carry an energy-dependent extrusion pump which is paradoxically activated by tesmilifene plus the chemotherapy. The result is that, despite the chemotherapy's remaining extracellular, the cell dies from reactive oxygen species leaking from the electron chain transport in the abnormal mitochondria which characterize cancer. These mitochondria are activated in response to the ATP cost of this pump activation, in these predominantly glycolytic cells.

Histamine-cytokine connection in immunity and hematopoiesis

A number of recent studies have led to a reappraisal of the functional capacities of histamine in immunity and hematopoiesis. This change of perspective was provided by the following findings: (1) the evidence for multiple cellular sources of histamine, differing from mature basophils and mast cells by their ability to newly synthesize and liberate the mediator without prior storage, (2) the discovery of a novel histamine receptor (H4R), preferentially expressed on hematopoietic and immunocompetent cells, (3) the potential intracellular activity of histamine through cytochrome P450 and (4) the demonstration of a histamine-cytokine cross-talk. Indeed, cytokines not only modulate the degranulation process of histamine but also control its neosynthesis by the histamine-forming enzyme, histidine decarboxylase (HDC), at transcriptional and post-transcriptional levels. In turn, histamine intervenes in the intricate cytokine network, regulating cytokine production by immune cells through distinct receptors signaling distinct biological effects. This type of regulation is particularly relevant in the context of TH1/TH2 differentiation, autoimmunity and tumor immunotherapy.

Molecular characterization of the microsomal tamoxifen binding site

Tamoxifen is a selective estrogen receptor modulator widely used for the prophylactic treatment of breast cancer. In addition to the estrogen receptor (ER), tamoxifen binds with high affinity to the microsomal antiestrogen binding site (AEBS), which is involved in ER-independent effects of tamoxifen. In the present study, we investigate the modulation of the biosynthesis of cholesterol in tumor cell lines by AEBS ligands. As a consequence of the treatment with the antitumoral drugs tamoxifen or PBPE, a selective AEBS ligand, we show that tumor cells produced a significant concentration- and time-dependent accumulation of cholesterol precursors. Sterols have been purified by HPLC and gas chromatography, and their chemical structures determined by mass spectrometric analysis. The major metabolites identified were 5alpha-cholest-8-en-3beta-ol for tamoxifen treatment and 5alpha-cholest-8-en-3beta-ol and cholesta-5,7-dien-3beta-ol, for PBPE treatment, suggesting that these AEBS ligands affect at least two enzymatic steps: the 3beta-hydroxysterol-Delta8-Delta7-isomerase and the 3beta-hydroxysterol-Delta7-reductase. Steroidal antiestrogens such as ICI 182,780 and RU 58,668 did not affect these enzymatic steps, because they do not bind to the AEBS. Transient co-expression of human 3beta-hydroxysterol-Delta8-Delta7-isomerase and 3beta-hydroxysterol-Delta7-reductase and immunoprecipitation experiments showed that both enzymes were required to reconstitute the AEBS in mammalian cells. Altogether, these data provide strong evidence that the AEBS is a hetero-oligomeric complex including 3beta-hydroxysterol-Delta8-Delta7-isomerase and the 3beta-hydroxysterol-Delta7-reductase as subunits that are necessary and sufficient for tamoxifen binding in mammary cells. Furthermore, because selective AEBS ligands are antitumoral compounds, these data suggest a link between cholesterol metabolism at a post-lanosterol step and tumor growth control. These data afford both the identification of the AEBS and give new insight into a novel molecular mechanism of action for drugs of clinical value.

Phase III Study of N,N-Diethyl-2-[4-(Phenylmethyl) Phenoxy]Ethanamine (BMS-217380-01) Combined With Doxorubicin Versus Doxorubicin Alone in Metastatic/Recurrent Breast Cancer: National Cancer Institute of Canada Clinical Trials Group Study MA.19

Purpose

N,N-diethyl-2-[4-(phenylmethyl)phenoxy]ethanamine (DPPE; tesmilifene) is a novel agent that augments chemotherapy cytotoxicity in vitro and in vivo. A phase II trial combining DPPE and doxorubicin (DOX) in metastatic breast carcinoma showed increased response over that expected with DOX. We report a phase III trial comparing DOX with DPPE plus DOX in metastatic or recurrent breast cancer.

Patients and Methods

Anthracycline-naive women with measurable metastatic disease were randomly assigned to receive, every 21 days, either DOX 60 mg/m2 intravenously or DOX during the last 20 minutes of an 80-minute infusion of DPPE (5.3 mg/kg), in both cases to cumulative DOX doses of 450 mg/m2. Patients receiving DPPE were aggressively premedicated to ameliorate toxicity. End points included progression-free survival (PFS), response rate (RR), and response duration (RD), quality of life (QOL), toxicity, and overall survival (OS).

Results

A planned interim analysis failed to detect an RR difference more than 5%. The study was closed to additional accrual and all DPPE was discontinued. The final analysis was conducted as planned after 256 progression events (median follow-up, 20.5 months). There was no significant difference in RR, RD, or PFS between arms. DPPE plus DOX was statistically superior to DOX in OS (hazard ratio, 0.66; 95% CI, 0.48 to 0.91; P = .021). DPPE plus DOX was associated with more gastrointestinal and CNS toxicity. No consistent influence on QOL was detected.

Conclusion

This study demonstrated no advantage in RR, RD, or PFS but significantly superior OS for DPPE plus DOX. Additional studies of DPPE are warranted.

Synthesis, binding and structure-affinity studies of new ligands for the microsomal anti-estrogen binding site (AEBS)

New compounds have been synthesized based on the structure of the anti-tumoral drug tamoxifen and its diphenylmethane derivative, N,N-diethyl-2-[(4-phenyl-methyl)-phenoxy]-ethanamine, HCl (DPPE). These new compounds have no affinity for the estrogen receptor (ER) and bind with various affinity to the anti-estrogen binding site (AEBS). Compounds 2, 10, 12, 13, 20a, 20b, 23a, 23b, 29 exhibited 1.1-69.5 higher affinity than DPPE, and compounds 23a and 23b have 1.2 and 3.5 higher affinity than tamoxifen. Three-dimensional structure analysis, performed using the intersection of the van der Waals volume occupied by tamoxifen in its crystallographic state and the van der Waals volume of these new compounds in their calculated minimal energy conformation, correlated well with their pKi for AEBS (r = 0.84, P<0.0001, n = 18). This is the first structure-affinity relationship (SAR) ever reported for AEBS ligands. Moreover in this study we have reported the synthesis of new compounds of higher affinity than the lead compounds and that are highly specific for AEBS. Since these compounds do not bind ER they will be helpful to study AEBS mediated cytotoxicity. Moreover our study shows that our strategy is a new useful guide to design high affinity and selective ligands for AEBS.