Anti-tumour efficacy on glioma models of PHA-848125, a multi-kinase inhibitor able to cross the blood-brain barrier

BACKGROUND AND PURPOSE

Malignant gliomas, the most common primary brain tumours, are highly invasive and neurologically destructive neoplasms with a very bad prognosis due to the difficulty in removing the mass completely by surgery and the limited activity of current therapeutic agents. PHA-848125 is a multi-kinase inhibitor with broad anti-tumour activity in pre-clinical studies and good tolerability in phase 1 studies, which could affect two main pathways involved in glioma pathogenesis, the G1-S phase progression control pathway through the inhibition of cyclin-dependent kinases and the signalling pathways mediated by tyrosine kinase growth factor receptors, such as tropomyosin receptors. For this reason, we tested PHA-848125 in glioma models.

EXPERIMENTAL APPROACH

PHA-848125 was tested on a panel of glioma cell lines in vitro to evaluate inhibition of proliferation and mechanism of action. In vivo efficacy was evaluated on two glioma models both as single agent and in combination with standard therapy.

KEY RESULTS

When tested on a subset of representative glioma cell lines, PHA-848125 blocked cell proliferation, DNA synthesis and inhibited both cell cycle and signal transduction markers. Relevantly, PHA-848125 was also able to induce cell death through autophagy in all cell lines. Good anti-tumour efficacy was observed by oral route in different glioma models both with s.c. and intracranial implantation. Indeed, we demonstrate that the drug is able to cross the blood-brain barrier. Moreover, the combination of PHA-848125 with temozolomide resulted in a synergistic effect, and a clear therapeutic gain was also observed with a triple treatment adding PHA-848125 to radiotherapy and temozolomide.

CONCLUSIONS AND IMPLICATIONS

All the pre-clinical data obtained so far suggest that PHA-848125 may become a useful agent in chemotherapy regimens for glioma patients and support its evaluation in phase 2 trials for this indication.

4'-Iodo-4'-deoxydoxorubicin disrupts the fibrillar structure of transthyretin amyloid

Transthyretin (TTR) is a tetrameric protein synthesized mainly by the liver and the choroid plexus, from where it is secreted into the plasma and the cerebrospinal fluid, respectively. Some forms of polyneuropathy, vitreopathy, and cardiomyopathy are caused by the deposition of normal and/or mutant TTR molecules in the form of amyloid fibrils. Familial amyloidotic polyneuropathy is the most common form of TTR amyloidosis related to the V30M variant. It is still unclear the process by which soluble proteins deposit as amyloid. The treatment of amyloid-related disorders might attempt the stabilization of the soluble protein precursor to retard or inhibit its deposition as amyloid; or aim at the resorption of the deposited amyloid. The anthracycline 4'-iodo-4'-deoxydoxorubicin (I-DOX) has been shown to reduce the amyloid load in immunoglobulin light-chain amyloidosis. We investigated 1) whether I-DOX has affinity for TTR amyloid in tissues, 2) determined the I-DOX binding constants to TTR synthetic fibrils, and 3) determined the nature of the effect of I-DOX on TTR fibrils. We report that 1) I-DOX co-localizes with amyloid deposits in tissue sections of patients with familial amyloidotic polyneuropathy; 2) I-DOX strongly interacts with TTR amyloid fibrils and presents two binding sites with k(d) of 1.5 x 10(-11) mol/L and 5.6 x 10(-10) mol/L, respectively; and 3) I-DOX disrupts the fibrillar structure of TTR amyloid into amorphous material, as assessed by electron microscopy but does not solubilize the fibrils as confirmed by filter assays. These data support the hypothesis that I-DOX and less toxic derivatives can prove efficient in the treatment of TTR-related amyloidosis.

Design and synthesis of functionalized glycomers as non-peptidic ligands for SH2 binding and as inhibitors of A-431 human epidermoid and HT-29 colon carcinoma cell lines

A set of O-substituted aryl beta-D-glucopyranosides were prepared and found to have inhibitory activity on the growth of two carcinoma cell lines.

Delivery of methoxymorpholinyl doxorubicin by interleukin 2-activated NK cells: effect in mice bearing hepatic metastases

The possibility of using interleukin 2 (IL-2)-activated natural killer cells (A-NK) to carry methoxymorpholinyl doxorubicin (MMDX; PNU 152243) to liver-infiltrating tumours was explored in mice bearing 2-day established M5076 reticulum cell sarcoma hepatic metastases. In vitro, MMDX was 5.5-fold more potent than doxorubicin against M5076 tumour cells. MMDX uptake by A-NK cells correlated linearly with drug concentration in the incubation medium [correlation coefficient (r) = 0.999]; furthermore, as MMDX incorporation was readily reproducible in different experiments, the amount of drug delivered by A-NK cells could be modulated. In vivo experiments showed that intravenous (i.v.) injection of MMDX-loaded A-NK cells exerted a greater therapeutic effect than equivalent or even higher doses of free drug. The increase in lifespan (ILS) following A-NK cell delivery of 53 microg kg(-1) MMDX, a dosage that is ineffective when administered in free form, was similar to that observed in response to 92 microg kg(-1) free drug, a dosage close to the 10% lethal dose (ILS 42% vs. 38% respectively). These results correlated with pharmacokinetic studies showing that MMDX encapsulation in A-NK cells strongly modifies its organ distribution and targets it to tissues in which IL-2 activated lymphocytes are preferentially entrapped after i.v. injection.

Interaction of the anthracycline 4'-iodo-4'-deoxydoxorubicin with amyloid fibrils: inhibition of amyloidogenesis

All types of amyloidosis are structurally characterized by the cross beta-pleated sheet conformation of the fibrils, irrespective of their biochemical composition. The clinical observation that the anthracycline 4'-iodo-4'-deoxy-doxorubicin (IDOX) can induce amyloid resorption in patients with immunoglobulin light chain amyloidosis was the starting point for this investigation of its possible mechanism of action. IDOX binds strongly to all five types of natural amyloid fibrils tested: immunoglobulin light chains, amyloid A, transthyretin (methionine-30 variant), beta-protein (Alzheimer), and beta 2-microglobulin. Quantitative binding studies showed that IDOX, but not doxorubicin, binds strongly to amyloid fibrils. This binding is saturable and involves two apparently distinct binding sites with Kd values of 5.9 x 10(-11) M and 3.4 x 10(-9) M. IDOX inhibited in vitro insulin amyloid fibrillogenesis. In vivo studies using the experimental amyloid murine model confirmed the specific targeting of IDOX to amyloid deposits. Preincubation of amyloid enhancing factor with IDOX significantly reduced the formation of amyloid deposits. It is hypothesized that IDOX exerts its beneficial effects through the inhibition of fibril growth, thus increasing the solubility of existing amyloid deposits and facilitating their clearance. IDOX may represent the progenitor of a class of amyloid-binding agents that could have both diagnostic and therapeutic potential in all types of amyloidoses.

Adoptive transfer of lymphokine-activated killer cells loaded with 4'-deoxy-4'-iododoxorubicin: therapeutic effect in mice bearing lung metastases

We studied the potential use of lymphokine-activated killer (LAK) cells loaded with 4'-deoxy-4'-iododoxorubicin (IDX) in adoptive immunotherapy experiments. Because LAK cells preferentially locate in the lung, we evaluated the therapeutic effect of IDX-loaded LAK cells in mice bearing lung metastases induced by B16F1 tumor cell injection. In vitro studies showed that LAK cells rapidly incorporated IDX, with maximum uptake at 15 min, followed by a plateau; drug efflux was initially rapid and then continued at a much slower rate. Evaluation of LAK cell cytotoxic activity against relevant target cells showed a 30% decrease after IDX treatment that progressed with time over the next 6 h. P388 tumor cell growth was inhibited by coculture with IDX-loaded LAK cells, thus demonstrating that the released IDX maintained its pharmacological activity. Finally, high performance liquid chromatography analysis of tissue IDX concentration revealed a considerably higher and long-lasting concentration in the lungs of mice receiving IDX-loaded LAK cells, compared to mice given injections of a comparable amount of free drug. Moreover, adoptive transfer of IDX-loaded LAK cells into tumor-bearing mice caused a significant reduction in the number of lung metastases versus control mice given injections of even higher doses of free drug.

Reversal of multidrug resistance by new dihydropyridines with low calcium antagonist activity

The clinical use of Ca++ antagonist agents as modulators of multidrug resistance is limited by their strong vasodilator activity. This study reports data obtained by testing a series of new 1,4 dihydropyridine derivatives (DHPs) for their in vitro resistance modulating activity and their Ca++ antagonist effect. All the tested DHPs are active to increase doxorubicin activity with dose modifying factor values ranging between 2 and 47 on P388/DX cells and 12 and 36 on LoVo/DX cells. Their resistance modulating action is exerted through an increase of DX intracellular level. The Ca++ antagonist activity of DHPs, evaluated as capacity to inhibit the KCl-induced contractions in isolated Guinea pig ileum strips, is not related to their resistance modulating activity. This finding makes it possible to select, for further in vivo evaluations, compounds IX, X and XI, which have strong ability to overcome multidrug resistance and low Ca++ antagonist effect.