Discovery of Ziresovir as a Potent, Selective, and Orally Bioavailable Respiratory Syncytial Virus Fusion Protein Inhibitor.

Ziresovir (RO-0529, AK0529) is reported here for the first time as a promising respiratory syncytial virus (RSV) fusion (F) protein inhibitor that currently is in phase 2 clinical trials. This article describes the process of RO-0529 as a potent, selective, and orally bioavailable RSV F protein inhibitor and highlights the in vitro and in vivo anti-RSV activities and pharmacokinetics in animal species. RO-0529 demonstrates single-digit nM EC50 potency against laboratory strains, as well as clinical isolates of RSV in cellular assays, and more than one log viral load reduction in BALB/c mouse model of RSV viral infection. RO-0529 was proven to be a specific RSV F protein inhibitor by identification of drug resistant mutations of D486N, D489V, and D489Y in RSV F protein and the inhibition of RSV F protein-induced cell-cell fusion in cellular assays.

Clinical Efficacy of Afatinib Treatment for a Patient with Leptomeningeal Carcinomatosis.

Leptomeningeal metastases occur in 1% of patients with non-small-cell lung cancer. There have been several reports on the treatment of leptomeningeal metastases with afatinib. Our patient was a 41-year-old woman who had never smoked and was diagnosed with stage IV adenocarcinoma of the lung with an epidermal growth factor receptor (EGFR) mutation. She was treated with afatinib for the recurrence of leptomeningeal metastases. After the treatment with afatinib was initiated, the neurological symptoms dramatically regressed, and she achieved progression-free survival for 7 months. The concentration of afatinib in the cerebrospinal fluid (CSF) ranged from 0.05 to 0.14 ng/mL, and the penetration rate of afatinib from the plasma to the CSF ranged from 0.28 to 0.40%. This concentration might be sufficient to achieve a clinical effect for leptomeningeal carcinomatosis. Therefore, afatinib administered at the usual doses may be an effective treatment for leptomeningeal carcinomatosis of EGFR-mutated or EGFR-tyrosine kinase inhibitor-sensitive lung adenocarcinoma.

Efficacy of afatinib, an irreversible ErbB family blocker, in the treatment of intracerebral metastases of non-small cell lung cancer in mice.

Few effective therapeutic options are currently available for the treatment of non-small cell lung cancer (NSCLC) with brain metastases (BM). Recent evidence shows that NSCLC patients with BMs respond well to afatinib, but little is known about the underlying mechanisms. In this study, we evaluated the efficacy of afatinib in treatment of BMs in mice and investigated whether afatinib could actively penetrate the brain-blood barrier and bind to its target. NSCLC BM model was established in nude mice by intracerebral injection of PC-9.luc cells. The tumors were measured weekly using in vivo quantitative bioluminescence. The mice are administrated afatinib (15, 30 mg·kg-1·d-1, ig) for 14 d. The antitumor efficacy of afatinib was determined by tumor growth inhibition (TGI), which was calculated as [1-(change of tumor volume in treatment group/control group)×100]. Pharmacokinetic characteristics were measure in mice receiving a single dose of afatinib (30 mg/kg, ig). Pharmacodynamics of afatinib was also assessed by detecting the expression of pEGFR (Tyr1068) in brain tumor foci using immunohistochemistry. Administration of afatinib (15, 30 mg·kg-1·d-1) dose-dependently inhibited PC-9 tumor growth in the brain with a TGI of 90.2% and 105%, respectively, on d 14. After administration of afatinib (30 mg/kg), the plasma concentration of afatinib was 91.4±31.2 nmol/L at 0.5 h, reached a peak (417.1±119.9 nmol/L) at 1 h, and was still detected after 24 h. The cerebrospinal fluid (CSF) concentrations followed a similar pattern. The T1/2 values of afatinib in plasma and CSF were 5.0 and 3.7 h, respectively. The AUC(0-24 h) values for plasma and CSF were 2375.5 and 29.1 nmol/h, respectively. The plasma and CSF concentrations were correlated (r=0.844, P<0.01). Pharmacodynamics study showed that the expression levels of pEGFR were reduced by 90% 1 h after afatinib administration. The Emax was 86.5%, and the EC50 was 0.26 nmol/L. A positive correlation between CSF concentrations and pEGFR modulation was revealed. Afatinib penetrates the BBB in NSCLC BM mice and contributes to the brain tumor response. The CSF exposure level is correlated with the plasma level, which in turn is correlated with the modulation of pEGFR in the tumor tissues. The results support for the potential application of afatinib in NSCLC patients with BMs.

EGFR mutation status of paired cerebrospinal fluid and plasma samples in EGFR mutant non-small cell lung cancer with leptomeningeal metastases.

PURPOSE: Central nervous system (CNS) is the prevalent site for metastases in epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI)-relapsed NSCLC patients. To understand the EGFR mutation status in paired cerebrospinal fluid (CSF) and plasma samples after EGFR-TKI treatment failure might be useful to guide the treatment of intra- and extracranial tumors in those patients. METHODS: Paired CSF and plasma samples were collected from seven NSCLC patients with CNS metastases after EGFR-TKI failure. EGFR mutations were tested by amplification refractory mutation system (ARMS) and droplet digital PCR (ddPCR) methods. Gefitinib concentrations were evaluated by high-performance liquid chromatography-mass spectrometry (HPLC-MS/MS). RESULTS: EGFR mutations were detected in all seven CSF samples, including three of E19-Del, three of L858R and one of E19-Del&T790M by both methods. On the other hand, majority of the matched plasma samples (5/7) were negative for EGFR mutations by both methods. The other two plasma samples were positive for E19-Del&T790M by ddPCR, and one of them had undetectable T790M by ARMS. Gefitinib concentration in CSF was much lower than that in plasma (mean CSF/plasma ratio: 1.8 %). CONCLUSIONS: After EGFR-TKI failure, majority of the NSCLC patients with CNS metastases remained positive detection of EGFR sensitive mutations in CSF, but much less detection in the matched plasma. Significantly low exposure of gefitinib in CSF might explain the intracranial protection of the EGFR sensitive mutation positive tumor cells.

Impact of whole brain radiation therapy on CSF penetration ability of Icotinib in EGFR-mutated non-small cell lung cancer patients with brain metastases: Results of phase I dose-escalation study.

OBJECTIVES: Whole-brain radiation therapy (WBRT) and epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) are both treatment options for EGFR-mutated non-small cell lung cancer (NSCLC) patients with brain metastases. However, the dose-escalation toxicity and efficacy of combination therapy, and the effect of WBRT on cerebrospinal fluid (CSF) penetration of EGFR-TKIs are still unclear. MATERIALS AND METHODS: EGFR-mutated NSCLC patients with brain metastases were enrolled in this study, and the cohorts were constructed with a 3+3 design. The patients received icotinib with escalating doses (125-625mg, tid), and the concurrent WBRT (37.5Gy/15f/3weeks) started a week later. The CSF penetration rates of icotinib were tested before, immediately after, and 4 weeks after WBRT, respectively. Potential toxicities and benefits from dose-escalation treatment were analyzed. RESULTS: Fifteen patients were included in this study, 3 at each dose level from 125mg-375mg and 6 at 500mg with 3 occurred dose-limiting toxicities. The maximal tolerated dose of icotinib was 375mg tid in this combination therapy. There was a significant correlation between icotinib concentration in the CSF and plasma (R(2)=0.599, P<0.001). The CSF penetration rate of icotinib, from 1.2% to 9.7%, reached a maximum at 375mg (median, 6.1%). There was no significant difference for CSF penetration rates among the three test points (median, 4.1% vs. 2.8% vs. 2.8%, P=0.16). The intracranial objective response rate and median intracranial progression free survival are 80% and 18.9 months. CONCLUSIONS: WBRT plus concurrent icotinib is well tolerated in EGFR-mutated NSCLC patients with brain metastases, up to an icotinib dose of 375mg tid. The icotinib CSF concentration seemed to have a potential ceiling effect with the dose escalation, and WBRT seemed to have no significant impact on CSF penetration of icotinib till 4 weeks after the treatment.

Whole-brain radiation fails to boost intracerebral gefitinib concentration in patients with brain metastatic non-small cell lung cancer: a self-controlled, pilot study.

PURPOSE: Whole-brain radiation therapy (WBRT) is generally considered as an efficient strategy to improve blood-brain barrier (BBB) permeability by damaging BBB structure and is therefore, used as a promising pretreatment of chemotherapy. However, the impact of radiotherapy on leaky BBB is still controversial for the reason that BBB of metastatic brain tumor lesion had been breached by tumor metastasizing. Herein, we conducted a self-controlled study to evaluate the effect of WBRT on the permeability of BBB in non-small cell lung cancer (NSCLC) patients with brain metastases (BM). METHOD: A prospective self-controlled research was performed. Radiation-naive NSCLC patients with BM were enrolled and treated with gefitinib for 2 weeks, and then concurrently combined with WBRT for 2 weeks. Plasma and cerebrospinal fluid (CSF) before and after WBRT were collected on day 15 and 29 after the initiation of gefitinib treatment. The concentrations of gefitinib in these samples were measured by HPLC. RESULTS: Three patients were enrolled and evaluated. The concentrations of gefitinib in plasma and CSF pre-WBRT were comparable to those of post-WBRT. Consequently, no significant change was noted in the CSF-to-plasma ratios of gefitinib before and after WBRT (2.79 ± 1.47 vs. 2.35 ± 1.74 %, p = 0.123). CONCLUSIONS: The WBRT may not affect the BBB permeability by determining the concentration of gefitinib in NSCLC patients with BM.

A phase II study of icotinib and whole-brain radiotherapy in Chinese patients with brain metastases from non-small cell lung cancer.

PURPOSE: Icotinib is a new first-generation epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors. A phase II study was conducted to evaluate the efficacy and safety of icotinib in combination with whole-brain radiotherapy (WBRT) in Chinese NSCLC patients with brain metastases (BMs); the cerebrospinal fluid (CSF)/plasma concentrations of icotinib were also investigated. METHODS: Eligible patients had BMs from NSCLC, regardless of the EGFR status. Icotinib was administered at 125 mg orally 3 times/day until tumor progression or unacceptable toxicity, concurrently with WBRT (3.0 Gy per day, 5 days per week, to 30 Gy). CSF and plasma samples were collected simultaneously from 10 patients. Icotinib concentrations in the CSF and plasma were measured by high-performance liquid chromatography coupled with tandem mass spectrometry. RESULTS: Twenty patients were enrolled. The median follow-up time was 20.0 months. The overall response rate was 80.0%. The median progression-free survival time was 7.0 months (95% CI 1.2-13.2 months), and the median survival time (MST) was 14.6 months (95% CI 12.5-16.7 months). Of the 18 patients with known EGFR status, the MST was 22.0 months for those with an EGFR mutation and was 7.5 months for those with wild-type EGFR (P = 0.0001). The CSF concentration and penetration rate of icotinib were 11.6 ± 9.1 ng/mL and 1.4 ± 1.1%, respectively. No patient experienced ≥grade 4 toxicity. CONCLUSIONS: Icotinib was well tolerated in combination with WBRT and showed efficacy in patients with BMs from NSCLC. This clinical benefit was related to the presence of activating EGFR mutations.

Highly sensitive HPLC-DAD method for the assay of gefitinib in patient plasma and cerebrospinal fluid: application to a blood-brain barrier penetration study.

The quantification of intracranial gefitinib (GEF) exposure is limited owing to the sensitivity of analytical equipment. Although mass spectrometry (MS) is the preferred method because of its high sensitivity, the equipment is not available in many laboratories, especially in developing Asian countries. In this paper, we developed a highly sensitive high performance liquid chromatography-diode array detector (HPLC-DAD) method for the assay of GEF in human cerebrospinal fluid (CSF) and plasma. GEF was extracted from CSF and plasma by solid-phase extraction and liquid-liquid extraction, respectively. The chromatographic separation was performed on a C18 column with gradient elution of 0.1% triethylamine solution and acetonitrile, then finally detected at 344 nm. This method was validated and proved to be highly sensitive with a lower limit of quantitation value of 0.11 ng/mL in CSF and 11 ng/mL in plasma. The blood-brain barrier penetration ratio of GEF ranged from 1.48 to 2.41%. This method provides a reliable MS-independent solution for the quantitation of GEF in patients' CSF and plasma.

Population pharmacokinetics/pharmacodynamics of erlotinib and pharmacogenomic analysis of plasma and cerebrospinal fluid drug concentrations in Japanese patients with non-small cell lung cancer.

BACKGROUND: Erlotinib shows large inter-patient pharmacokinetic variability, but the impact of early drug exposure and genetic variations on the clinical outcomes of erlotinib remains fully investigated. The primary objective of this study was to clarify the population pharmacokinetics/pharmacodynamics of erlotinib in Japanese patients with non-small cell lung cancer (NSCLC). The secondary objective was to identify genetic determinant(s) for the cerebrospinal fluid (CSF) permeability of erlotinib and its active metabolite OSI-420. METHODS: A total of 88 patients treated with erlotinib (150 mg/day) were enrolled, and CSF samples were available from 23 of these patients with leptomeningeal metastases. Plasma and CSF concentrations of erlotinib and OSI-420 were measured by high-performance liquid chromatography with UV detection. Population pharmacokinetic analysis was performed with the nonlinear mixed-effects modelling program NONMEM. Germline mutations including ABCB1 (1236C>T, 2677G>T/A, 3435C>T), ABCG2 (421C>A), and CYP3A5 (6986A>G) polymorphisms, as well as somatic EGFR activating mutations if available, were examined. Early exposure to erlotinib and its safety/efficacy relationship were evaluated. RESULTS: The apparent clearance of erlotinib and OSI-420 were significantly decreased by 24 and 35 % in patients with the ABCG2 421A allele, respectively (p < 0.001), while ABCB1 and CYP3A5 polymorphisms did not affect their apparent clearance. The ABCG2 421A allele was significantly associated with increased CSF penetration for both erlotinib and OSI-420 (p < 0.05). Furthermore, the incidence of grade ≥2 diarrhea was significantly higher in patients harboring this mutant allele (p = 0.035). A multivariate logistic regression model showed that erlotinib trough (C0) levels on day 8 were an independent risk factor for the development of grade ≥2 diarrhea (p = 0.037) and skin rash (p = 0.031). Interstitial lung disease (ILD)-like events occurred in 3 patients (3.4 %), and the median value of erlotinib C0 levels adjacent to these events was approximately 3 times higher than that in patients who did not develop ILD (3253 versus 1107 ng/mL; p = 0.014). The objective response rate in the EGFR wild-type group was marginally higher in patients achieving higher erlotinib C0 levels (≥1711 ng/mL) than that in patients having lower erlotinib C0 levels (38 versus 5 %; p = 0.058), whereas no greater response was observed in the higher group (67 %) versus the lower group (77 %) within EGFR mutation-positive patients (p = 0.62). CONCLUSIONS: ABCG2 can influence the apparent clearance of erlotinib and OSI-420, and their CSF permeabilities in patients with NSCLC. Our preliminary findings indicate that early exposure to erlotinib may be associated with the development of adverse events and that increased erlotinib exposure may be relevant to the antitumor effects in EGFR wild-type patients while having less of an impact on the tumor response in EGFR mutation-positive patients.

Cerebrospinal fluid concentrations of gefitinib in patients with lung adenocarcinoma.

BACKGROUND: Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs), such as gefitinib and erlotinib, have high response and disease control rates in patients with central nervous system (CNS) metastases. However there have been only a few case reports on the penetration of gefitinib into the cerebrospinal fluid (CSF). The aim of this study was to investigate the CSF concentration of gefitinib in Chinese patients with lung adenocarcinomas. METHODS: From March 2007 to December 2010, 22 patients were sequentially enrolled in this study at Peking Union Medical College Hospital (PUMCH). CSF and plasma samples were collected at the same time from each patient after at least 7 doses of gefitinib. The concentrations of gefitinib in the CSF and plasma were measured by high performance liquid chromatography coupled with tandem mass spectrometry. The clinical factors that may affect gefitinib penetration were analyzed. RESULTS: The mean plasma and CSF concentrations of gefitinib were 491.8 ± 184.2 ng/mL and 6.2 ± 4.6 ng/mL, respectively, and the mean ratio of CSF-plasma concentration was 1.3% ± 0.7%. There was a good correlation between CSF and plasma gefitinib concentrations (R = 0.556, P = .006). The presence of CNS metastases was associated with increased gefitinib CSF penetration (1.46% vs. 0.95%; P = .042). CONCLUSIONS: The concentration of gefitinib in CSF was low, and it was significantly related to the plasma gefitinib concentration. Because of the inadequate CNS drug exposure, patients in whom the extracranial lesions were well controlled may benefit from increasing gefitinib dose for the new intracranial lesions.

Quantitative evaluation of the impact of active efflux by p-glycoprotein and breast cancer resistance protein at the blood-brain barrier on the predictability of the unbound concentrations of drugs in the brain using cerebrospinal fluid concentration as a surrogate.

This study investigated the impact of the active efflux mediated by P-glycoprotein (P-gp) and breast cancer resistance protein (Bcrp) at the blood-brain barrier (BBB) on the predictability of the unbound brain concentration (C(u,brain)) by the concentration in the cerebrospinal fluid (CSF) (C(u,CSF)) in rats. C(u,brain) is obtained as the product of the total brain concentration and unbound fraction in the brain (f(u,brain)) determined in vitro in brain slices. Twenty-five compounds, including P-gp and/or Bcrp substrates, were given a constant intravenous infusion, and their plasma, brain, and CSF concentrations were determined. P-gp and/or Bcrp substrates, such as verapamil, loperamide, flavopiridol, genistein, quinidine, dantrolene, daidzein, cimetidine, and pefloxacin, showed a higher CSF-to-brain unbound concentration ratio (K(p,uu,CSF/brain)) compared with non-P-gp and non-Bcrp substrates. K(p,uu,CSF/brain) values of P-gp-specific (quinidine and verapamil) and Bcrp-specific (daidzein and genistein) substrates were significantly decreased in Mdr1a/1b(-/-) and Bcrp(-/-) mice, respectively. Furthermore, consistent with the contribution of P-gp and Bcrp to the net efflux at the BBB, K(p,uu,CSF/brain) values of the common substrates (flavopiridol and erlotinib) were markedly decreased in Mdr1a/1b(-/-)/Bcrp(-/-) mice, but only moderately or weakly in Mdr1a/1b(-/-) mice and negligibly in Bcrp(-/-) mice. In conclusion, predictability of C(u,brain) by C(u,CSF) decreases along with the net transport activities by P-gp and Bcrp at the BBB. C(u,CSF) of non-P-gp and non-Bcrp substrates can be a reliable surrogate of C(u,brain) for lipophilic compounds.

Determination of vandetanib in human plasma and cerebrospinal fluid by liquid chromatography electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS).

A sensitive and precise LC-ESI-MS/MS method for the determination of vandetanib (ZD6474) in human plasma and cerebrospinal fluid (CSF) using [(13)C,d(3)]-ZD6474 as an internal standard (ISTD) was developed and validated. Sample preparation consisted of a simple liquid-liquid extraction with tert-butyl methyl ether containing 0.1% or 0.5% ammonium hydroxide. ZD6474 and ISTD were separated on a Kinetex C18 column (2.6 µm, 50 mm × 2.1 mm) at ambient temperature with an isocratic mobile phase (acetonitrile/10mM ammonium formate=50/50, v/v, at pH 5.0) delivered at 0.11 mL/min. The retention time of both compounds was at 1.60 min in a runtime of three min. Detection was achieved by an API-3200 LC-MS/MS system, monitoring m/z 475.1/112.1 and m/z 479.1/116.2 for vandetanib and ISTD, respectively. The method was linear in the range of 0.25-50 ng/mL (R(2) ≥ 0.990) for the CSF curve and from 1.0 to 3000 ng/mL (R(2) ≥ 0.992) for the plasma curve. The mean recovery for vandetanib was 80%. Within-day and between-day precisions were ≤ 8.8% and ≤ 5.9% for CSF and plasma, respectively. Within-day and between-day accuracies ranged from 95.0 to 98.5% for CSF, and from 104.0 to 108.5% for plasma. Analysis of plasma from six different sources showed no matrix effect for vandetanib (MF=0.98, %CV ≤ 4.97, n=6). This method was successfully applied to the analysis of pharmacokinetic samples from children with brain tumors treated with oral vandetanib.

Erlotinib efficacy and cerebrospinal fluid concentration in patients with lung adenocarcinoma developing leptomeningeal metastases during gefitinib therapy.

PURPOSE: We have treated patients with non-small-cell lung cancer (NSCLC) who developed leptomeningeal metastases (LM) during gefitinib therapy, and then found symptomatic improvement following treatment change to erlotinib. Based on this experience, we wondered whether erlotinib could be detected in cerebrospinal fluid (CSF) when it was used for NSCLC patients with LM. This study was conducted to determine erlotinib concentrations in CSF and assess responses to erlotinib in patients with NSCLC developing LM during gefitinib therapy. METHODS: Three advanced NSCLC patients with LM that developed during gefitinib therapy were treated with erlotinib. On day 28 after the initiation of erlotinib treatment, plasma and CSF were obtained and the concentrations of erlotinib in these samples were measured. Eastern Cooperative Oncology Group (ECOG) performance status (PS) and neurologic symptoms were determined. RESULTS: Erlotinib CSF penetration was 6.3% ± 6.1% (mean ± SD). In cases 1 and 2, we observed improvements in ECOG PS and neurologic symptoms. In case 3, cytological improvement was seen in the CSF. In each patient, deletion of exon 19 or exon 21 L858R mutation of the epidermal growth factor receptor (EGFR) gene was detected in carcinoma cells from the CSF. CONCLUSIONS: We report on 3 patients with NSCLC who had developed LM during gefitinib treatment and showed clinical improvements following change to erlotinib therapy. In all cases, small but measurable penetration of erlotinib into CSF was observed. Because EGFR mutations were detected in all cases, we suggest that erlotinib is a therapeutic option for LM carcinoma cells with EGFR mutations.

Cerebrospinal fluid concentration of erlotinib and its active metabolite OSI-420 in patients with central nervous system metastases of non-small cell lung cancer.

BACKGROUND: Although there have been several reports in which central nervous system (CNS) metastases of non-small cell lung cancer (NSCLC) were improved by erlotinib, cerebrospinal fluid (CSF) penetration of erlotinib in such patients has not been reported. We investigated CSF concentrations of erlotinib and its active metabolite OSI-420. METHOD: We administered 150 mg erlotinib daily to four patients with NSCLC who had CNS metastases, and we investigated plasma pharmacokinetics of erlotinib and OSI-420 on days 1 and 8. In addition, we measured the concentrations of erlotinib and OSI-420 in CSF just before administration of erlotinib on day 8. RESULTS: In all cases except for one case, plasma pharmacokinetics data on day 8 were similar to those previously reported. The mean +/- SD CSF concentrations of erlotinib and OSI-420 were 54 +/- 30 ng/ml and 10.8 +/- 8.2 ng/ml, respectively. The mean +/- SD CSF penetration rates of erlotinib and OSI-420 were 5.1% +/- 1.9% and 5.8% +/- 3.6%, respectively. CSF concentrations of erlotinib exceeded median inhibitory concentration (IC50) of erlotinib in intact tumor cells with wild-type epidermal growth factor receptor gene. CONCLUSION: The CSF penetrations of erlotinib and OSI-420 in patients with NSCLC who had CNS metastases were approximately 5.1% and 5.8%, respectively. This indicates that erlotinib can become a treatment option for CNS metastases of NSCLC.

High dose weekly erlotinib achieves therapeutic concentrations in CSF and is effective in leptomeningeal metastases from epidermal growth factor receptor mutant lung cancer.

Leptomeningeal metastases (LM) occur in 5-10% of patients with solid tumors and are associated with a dismal prognosis. We describe LM from lung adenocarcinoma harboring a mutation in the epidermal growth factor receptor (EGFR) gene that confers sensitivity to the EGFR tyrosine kinase inhibitors (EGFR-TKIs) erlotinib and gefitinib. The CSF concentration of EGFR-TKIs achieved by standard daily dosing may be insufficient for therapeutic effect. However, intermittent (pulsatile) high dose administration (1000-1500 mg/week) achieves a higher CSF concentration than standard dosing, and successfully controlled LM in this patient.

The plasma and cerebrospinal fluid pharmacokinetics of erlotinib and its active metabolite (OSI-420) after intravenous administration of erlotinib in non-human primates.

PURPOSE: Erlotinib hydrochloride is a small molecule inhibitor of epidermal growth factor receptor (EGFR). EGFR is over-expressed in primary brain tumors and solid tumors that metastasize to the central nervous system. We evaluated the plasma and cerebrospinal fluid (CSF) pharmacokinetics of erlotinib and its active metabolite OSI-420 after an intravenous (IV) dose in a non-human primate model. METHODS: Erlotinib was administered as a 1 h IV infusion to four adult rhesus monkeys. Serial blood and CSF samples were drawn over 48 h and erlotinib and OSI-420 were quantified with an HPLC/tandem mass spectroscopic assay. Pharmacokinetic parameters were estimated using non-compartmental and compartmental methods. CSF penetration was calculated from the AUC(CSF):AUC(plasma). RESULTS: Erlotinib disappearance from plasma after a short IV infusion was biexponential with a mean terminal half-life of 5.2 h and a mean clearance of 128 ml/min per m(2). OSI-420 exposure (AUC) in plasma was 30% (range 12-59%) of erlotinib, and OSI-420 clearance was more than 5-fold higher than erlotinib. Erlotinib and OSI-420 were detectable in CSF. The CSF penetration (AUC(CSF):AUC(plasma)) of erlotinib and OSI-420 was <5% relative to total plasma concentration, but CSF drug exposure was approximately 30% of plasma free drug exposure, which was calculated from published plasma protein binding values. The IV administration of erlotinib was well tolerated. CONCLUSIONS: Erlotinib and its active metabolite OSI-420 are measurable in CSF after an IV dose. The drug exposure (AUC) in the CSF is limited relative to total plasma concentrations but is substantial relative the free drug exposure in plasma.

Plasma and cerebrospinal fluid pharmacokinetics of erlotinib and its active metabolite OSI-420.

PURPOSE: To report cerebrospinal fluid (CSF) penetration of erlotinib and its metabolite OSI-420. EXPERIMENTAL DESIGN: Pharmacokinetic measurements were done in plasma (days 1, 2, 3, and 8 of therapy) and, concurrently, in plasma and CSF (before and at 1, 2, 4, 8, and 24 h after dose on day 34 of therapy) in an 8-year-old patient diagnosed with glioblastoma who received local irradiation and oral erlotinib in a phase I protocol. CSF samples were collected from a ventriculoperitoneal shunt, which was externalized because of infection. Erlotinib concentrations were determined by liquid chromatography/mass spectrometry. CSF penetration of erlotinib and OSI-420 were estimated by a compartmental model and by calculating the ratio of CSF to plasma 24-h area under concentration-time curve (AUC(0-24)). RESULTS: This patient was assigned to receive erlotinib at a dose level of 70 mg/m(2), but the actual daily dose was 75 mg (78 mg/m(2)). Erlotinib and OSI-420 plasma pharmacokinetic variables on days 8 and 34 overlapped to suggest that steady state had been reached. Whereas erlotinib and OSI-420 AUC(0-24) in plasma on day 34 were 30,365 and 2,527 ng h/mL, respectively, the correspondent AUC(0-24) in the CSF were 2,129 and 240 ng h/mL, respectively. Erlotinib and OSI-420 CSF penetration were 7% and approximately 9%, respectively, using both estimate methods. The maximum steady-state CSF concentration of erlotinib was approximately 130 ng/mL (325 nmol/L). CONCLUSIONS: The plasma pharmacokinetics of erlotinib in this child overlapped with results described in adults. Oral administration of erlotinib achieves CSF concentrations comparable with those active against several cancer cell lines in preclinical models.

The plasma pharmacokinetics and cerebrospinal fluid penetration of the thymidylate synthase inhibitor raltitrexed (Tomudex) in a nonhuman primate model.

PURPOSE: Raltitrexed (Tomudex), ZD1694) is a novel quinazoline folate analog that selectively inhibits thymidylate synthase. Intracellularly, raltitrexed is polyglutamated to its active form which can be retained in cells for prolonged periods. The pharmacokinetics of raltitrexed in plasma and cerebrospinal fluid (CSF) were studied in a nonhuman primate model. METHODS: Animals received 3 mg/m(2) (n = 1), 6 mg/m(2) (n = 3), or 10 mg/m(2) (n = 3) i.v. over 15 min, and frequent plasma samples were obtained over 48 h. CSF samples were drawn from an indwelling 4th ventricular Ommaya reservoir over 48 h. Plasma and CSF raltitrexed concentrations were measured with a novel, sensitive enzyme inhibition assay with a lower limit of quantification of 0.005 microM. A three-compartment pharmacokinetic model was fitted to the raltitrexed plasma concentration-time data. RESULTS: The plasma concentration-time profile of raltitrexed was triexponential with a rapid initial decline and a prolonged terminal elimination phase (t(1/2) > 24 h), which was related to retention of raltitrexed in a deep tissue compartment. At the peak approximately 30% of the administered dose was in the deep tissue compartment, and 24 h after the dosing >20% of the administered dose remained in the body with >99% in the deep tissue compartment. The mean peak (end of infusion) plasma concentrations after the 3, 6, and 10 mg/m(2) doses were 1.5, 2.4 and 4.8 microM, respectively. The clearance of raltitrexed ranged from 110 to 165 ml/min per m(2), and the steady-state volume of distribution exceeded 200 l/m(2). The CSF penetration of raltitrexed was limited (0.6 to 2.0%) and drug could only be detected in the CSF following a 10 mg/m(2 )dose. CONCLUSIONS: The elimination of raltitrexed is triexponential with a prolonged terminal elimination phase. The pharmacokinetic profile is consistent with extensive polyglutamation and intracellular retention of ralitrexed. The three-compartment model presented here may be useful for the analysis of the pharmacokinetics of raltitrexed in humans.

Pharmacology and toxicity of a potent "nonclassical" 2,4-diamino quinazoline folate antagonist, trimetrexate, in normal dogs.

The pharmacology of trimetrexate (JB-11, NSC 249008, 2,4-diamino-5-methyl-5-[(3,4,5-trimethoxyanilino)methyl]quinazoline), an antitumor agent effective against several mouse tumors, was studied in normal dogs. A high-performance liquid chromatographic technique with electrochemical detection, dihydrofolate reductase inhibition assay, and 14C-labeled drug were used to measure plasma disappearance, tissue distribution, excretion, and metabolism of the drug at doses from 0.5 to 6 mg/kg. Doses of 2 mg/kg were well tolerated without toxicity. Higher doses (3 to 6 mg/kg) produced mainly intestinal toxicity without significant hematological or liver abnormalities. The 6-mg/kg dose caused severe bloody diarrhea. After administration of 3 mg/kg, plasma concentrations of trimetrexate were 1 microM and were equal to or greater than 0.1 microM at 1 and 24 hr, respectively. The predominant pharmacokinetics of trimetrexate plasma disappearance was an elimination phase with a t1/2 of 3.5 hr. Concentrations in the cerebrospinal fluid were 2 to 5% of that in plasma and were maximum within 1 to 2 hr after i.v. administration. Highest tissue concentrations of drug were measured in liver and kidney; lowest were found in brain and lung. A dose equivalent to 3 mg/kg in humans (on a sq m basis) should produce adequate plasma concentrations (greater than 0.1 microM) for therapeutic effects.