Effects of rifampicin on antineoplastic drug pyrotinib maleate pharmacokinetics in healthy subjects.

PURPOSE: Pyrotinib (PTN), an irreversible EGFR/HER2 dual tyrosine kinase inhibitor used for treating HER2-positive breast cancer, is primarily metabolized by cytochrome P450 (CYP)3A4 isozyme. Rifampicin (RIF) is a strong index CYP3A4 inducer. Therefore, the study aimed to elucidate the effect of RIF on PTN pharmacokinetics (PK) in Chinese healthy volunteers. METHODS: This phase I, open-label study investigated the effects of steady-state RIF administration on single-dose PK of PTN. 18 healthy participants were enrolled in this trial, who received a single oral dose of 400 mg of PTN on days 1 and 13, and were administrated with RIF 600 mg qd on days 6 through 16. RIF was administrated on an empty stomach, PTN were administrated orally in the morning 30 min after the start of the standard meal. Serial PK samples for PTN were collected on days 1 and days 13. Safety assessments were performed via clinical laboratory tests throughout the study. RESULTS: 18 subjects were enrolled and 16 completed the study. RIF significantly reduced PTN exposure: Geometric least-squares mean ratios (90% CI) for PTN + RIF versus PTN alone were 0.04 (0.034,0.049), 0.04 (0.037,0.054), and 0.11 (0.09,0.124) for area under the curve from time zero to time of last quantifiable concentration (AUC0 - t), area under the curve from time zero to infinity (AUC0-∞ ), and maximum observed plasma concentration(Cmax), respectively. PTN alone and co-administered with RIF was well tolerated. CONCLUSION: The exposure of PTN was significantly affected by the action of RIF. The findings suggest that concomitant strong CYP3A4 inducers should be avoided during PTN treatment. Concurrent administration of PTN and RIF was well tolerated.

Mechanisms and pharmacokinetic/pharmacodynamic profiles underlying the low nephrotoxicity and ototoxicity of etimicin.

Etimicin (ETM), a fourth-generation aminoglycosides (AGs), is now widely clinically used in China due to its high efficacy and low toxicity. However, the mechanisms underlying its low nephrotoxicity and ototoxicity remain unclear. In the present study we compared the antibacterial and toxicity profiles of etimicin, gentamicin (GM, a second-generation AG), and amikacin (AMK, a third-generation AG), and investigated their pharmacokinetic properties in the toxicity target organs (kidney and inner ear) and subcellular compartments. We first demonstrated that ETM exhibited superior antibacterial activities against clinical isolates to GM and AMK, and it exerted minimal nephrotoxicity and ototoxicity in rats following multi-dose administration. Then, we conducted pharmacokinetic studies in rats, showed that the three AGs accumulated in the kidney and inner ear with ETM being distributed to a lesser degree in the two toxicity target organs as compared with GM and AMK high-dose groups. Furthermore, we conducted in vitro experiments in NRK-52E rat renal tubular epithelial cells and HEI-OC1 cochlear hair cells, and revealed that all the three AGs were distributed predominantly in the mitochondria with ETM showing minimal accumulation; they not only directly inhibited the activity of mitochondrial complexes IV and V but also inhibited mitochondrial function and its related PGC-1α-NRF1-TFAM pathway; ETM caused minimal damage to the mitochondrial complex and mitochondrial biogenesis. Our results demonstrate that the minimal otonephrotoxicity of ETM results from its lesser accumulation in mitochondria of target cells and subsequently lesser inhibition of mitochondrial function. These results provide a new strategy for discovering novel AGs with high efficacy and low toxicity.

Apatinib, a selective VEGFR2 inhibitor, improves the delivery of chemotherapeutic agents to tumors by normalizing tumor vessels in LoVo colon cancer xenograft mice.

Tumor vascular normalization has been proposed as a therapeutic strategy for malignant neoplasms, which can also interpret the synergistic effect of anti-angiogenesis agents combined with chemotherapy. Apatinib (Apa), a highly selective VEGFR2 inhibitor, attracts much attentions due to its encouraging anticancer activity, especially in the clinical trials of combined treatment. In this study, we investigated whether Apa could promote vascular normalization in tumor in a certain time window. Mice bearing LoVo colon cancer xenograft were orally administrated Apa (150 mg kg-1 per day) for 5, 7, 10, or 12 days. Apa significantly inhibited tumor growth and decreased the microvessel density. Using multi-photon microscopy and electron microscopy, we found that Apa improved tumor vessel morphology by pruning distorted vessel branches and decreased the gap between endothelial cells after a 7-day treatment. Furthermore, Apa decreased vessel leakage and increased pericyte coverage on vascular endothelial cells, suggesting that tumor vessels were more mature and integrated. The intratumoral distribution of adriamycin (ADR) in Apa group was improved from day 7 to 10 without change in plasma drug concentration. Tumor blood perfusion was also increased in this window, and the expression of hypoxia induced factor 1α was downregulated, suggesting the effect of Apa on alleviating tumor hypoxic micro-environment. In conclusion, Apa may improve the effective perfusion of tumor vessels and increase the intratumoral distribution of ADR in a certain time window via normalizing tumor vessels. This normalization window (7 to 10 days of treatment) may contribute to develop a regimen of combined medication in clinic use of Apa.