Biomedical subjects

Jaap Verweij

Publications and source records attributed to Jaap Verweij.

114 records · Page 7Linked to original sources

PubMed2002

Structural identification and biological activity of 7-methyl-10,11-ethylenedioxy-20(S)-camptothecin, a photodegradant of lurtotecan.

An additional chromatographic peak was observed in plasma samples of patients receiving NX 211, a liposomal formulation of the topoisomerase I inhibitor lurtotecan. We have isolated and purified this product by sequential solid-phase extractions, and we report its structure and cytotoxicity relative to lurtotecan and related agents. Nuclear magnetic resonance data indicate that cleavage of the piperazino moiety occurred at the N-C bond of the B-ring, yielding 7-methyl-10,11-ethylenedioxy-20(S)-camptothecin (MEC). Tests of the growth inhibition potential of MEC in seven human tumor cell lines showed that the compound was approximately 2-18-fold more cytotoxic than lurtotecan, topotecan, and 7-ethyl-10-hydroxy-20(S)-camptothecin (SN-38). Subsequently, we found that MEC was the product of rapid photolysis of lurtotecan, with the rate of degradation inversely proportional to NX 211 concentrations, and greatly depends on light intensity. Furthermore, MEC concentrations were found to increase significantly in plasma samples exposed to laboratory light but not in blood. MEC was not produced from NX 211 in the presence of human liver microsomes, suggesting that it is not a product of cytochrome P-450 metabolism. Using a validated analytical method, trace levels of MEC were quantitated in blood samples of two patients. These observations confirm that the precautions for protection from light currently specified for preparation and administration of NX 211 dose solutions are critical. Procedures to minimize formation of MEC, by the use of amber vials for NX 211 and by preparation of dilutions immediately before clinical use in a fashion completely protected from light, are now being routinely implemented.

Adult↗

PubMed2002

Influence of Cremophor El on the bioavailability of intraperitoneal paclitaxel.

It has been hypothesized that the paclitaxel vehicle Cremophor EL (CrEL) is responsible for nonlinear drug disposition by micellar entrapment. To gain further insight into the role of CrEL in taxane pharmacology, we studied the pharmacokinetics of paclitaxel in the presence and absence of CrEL after i.p. and i.v. dosing. Patients received an i.p. tracer dose of [G-(3)H]paclitaxel in ethanol without CrEL (100 microCi diluted further in isotonic saline) on day 1, i.p. paclitaxel formulated in CrEL (Taxol; 125 mg/m(2)) on day 4, an i.v. tracer of [G-(3)H]paclitaxel on day 22, and i.v. Taxol (175 mg/m(2)) on day 24. Four patients (age range, 54-74 years) were studied, and serial plasma samples up to 72 h were obtained and analyzed for total radioactivity, paclitaxel, and CrEL. In the presence of CrEL, i.v. paclitaxel clearance was 10.2 +/- 3.76 liters/h/m(2) (mean +/- SD), consistent with previous findings. The terminal disposition half-life was substantially prolonged after i.p. dosing (17.0 +/- 11.3 versus 28.7 +/- 8.72 h), as was the mean residence time (7.28 +/- 2.76 versus 40.7 +/- 13.8 h). The bioavailability of paclitaxel was 31.4 +/- 5.18%, indicating insignificant systemic concentrations after i.p. treatment. CrEL levels were undetectable after i.p. dosing (<0.05 microl/ml), whereas after i.v. dosing, the mean clearance was 159 +/- 58.4 ml/h/m(2), in line with earlier observations. In the absence of CrEL, the bioavailability and systemic concentrations of i.p. paclitaxel were significantly increased. This finding is consistent with the postulated concept that CrEL is largely responsible for the pharmacokinetic advantage for peritoneal cavity exposure to total paclitaxel compared with systemic delivery.

Aged↗

PubMed2002

Sarcomas.

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Animals↗

PubMedDate not supplied

Progression-free survival in gastrointestinal stromal tumours with high-dose imatinib: randomised trial.

BACKGROUND: Imatinib is approved worldwide for use in gastrointestinal stromal tumours (GIST). We aimed to assess dose dependency of response and progression-free survival with imatinib for metastatic GIST. METHODS: 946 patients were randomly allocated imatinib 400 mg either once or twice a day. Those assigned the once a day regimen who had progression were offered the option of crossover. The primary endpoint was progression-free survival. Analysis was by intention to treat. FINDINGS: At median follow-up of 760 days (IQR 644-859), 263 (56%) of 473 patients allocated imatinib once a day had progressed compared with 235 (50%) of 473 who were assigned treatment twice a day (estimated hazard ratio 0.82 [95% CI 0.69-0.98]; p=0.026). Side-effects arose in 465/470 (99%) patients allocated the once daily regimen compared with 468/472 (99%) assigned treatment twice a day. By comparison with the group treated once a day, more dose reductions (77 [16%] vs 282 [60%]) and treatment interruptions (189 [40%] vs 302 [64%]) were recorded in patients allocated the twice daily regimen, but treatment in both arms was fairly well tolerated. 52 (5%) patients achieved a complete response, 442 (47%) a partial response, and 300 (32%) stable disease, with no difference between groups. Median time to best response was 107 days (IQR 58-172). INTERPRETATION: If response induction is the only aim of treatment, a daily dose of 400 mg of imatinib is sufficient; however, a dose of 400 mg twice a day achieves significantly longer progression-free survival.

Aged↗

PubMedDate not supplied

Using single-agent therapy in adult patients with advanced soft tissue sarcoma can still be considered standard care.

The group of soft tissue sarcomas in adult patients is a heterogeneous group with more than 40 different subtypes. While local treatment remains the mainstay for localized disease, systemic chemotherapy can importantly contribute in the treatment of advanced soft tissue sarcoma. For patients with metastatic disease, chemotherapy is a palliative treatment in the vast majority of the cases. In this setting, toxicity should not outweigh the potential benefits resulting from chemotherapy. In patients with locally advanced disease too extensive for local treatment, systemic chemotherapy can contribute to cure, provided that tumor shrinkage renders subsequent optimal local treatment possible. In these cases, chemotherapeutic regimens yielding the highest response rates achievable should be used. In the last decades, several randomized studies have aimed to determine whether combination regimens yield benefit over single-agent treatment in terms of response rate and overall survival. This review addresses the current available data on chemotherapy for adult patients with soft tissue sarcoma, excluding gastrointestinal stromal tumor, the Ewing-like sarcomas, and other small blue round cell tumors. In addition, it is increasingly recognized that future research in soft tissue sarcoma should focus on the identification of tumor factors that can serve as targets for treatment and that the diverse tumor subtypes should be analyzed separately for their sensitivity to systemic treatment. This review also focuses on these and other strategies that will hopefully lead to better out comes in this disease entity in the near future.

Adult↗

PubMedDate not supplied

Complementary and alternative medicine during cancer treatment: beyond innocence.

Nowadays, complementary and alternative medicine (CAM) is popular all over the world. Billions of dollars are spent in this booming business. For several reasons, young, female, educated, and higher socioeconomic class cancer patients, in particular, have shown interest in these agents. Unfortunately, besides direct (and sometimes serious) side effects, several CAM ingredients are capable of interfering with the metabolism of concurrently used drugs, which may render the therapeutic outcome of the subscribed drug unpredictable. In the case of anticancer drugs, with their usually narrow therapeutic window, this may have dramatic consequences and can lead to unacceptable toxicities in some cases or decreased therapeutic activity in others. Therefore, cancer patients should be warned for these possible interactions and be advised to discuss CAM use openly with their treating physician. The general concept that natural products are harmless should thus be changed into a more realistic and responsible attitude. A tightened legislation and regulation (including Internet advertising and sales) could play a crucial role in this awareness process. This should finally enable safe exploration of the potential advantageous aspects of CAM, while living with cancer.

Complementary Therapies↗