Pemetrexed

Pemetrexed is a novel antifolate, the Ki values of the pentaglutamate of LY231514 are 1.3, 7.2, and 65 nM for inhibits thymidylate synthase (TS), dihydrofolate reductase (DHFR), and glycinamide ribonucleotide formyltransferase (GARFT), respectively.

In Vitro:Pemetrexed (LY231514) disodium is a novel classical antifolate, the antitumor activity of which may result from simultaneous and multipie inhibition of several key folate-requiring enzymes via its polyglutamated metabolites. Pemetrexed (LY231514) is one of the best substrates that is known for the enzyme FPGS (Km=1.6 μM and Vmax/Km=621). It is likely that polyglutamation and the polyglutamated metabolites of LY231514 play profound roles in determining both the selectivity and the antitumor activity of this novel agent. Whereas LY23l5l4 only moderately inhibits TS (Ki=340 nM, recombinant mouse), the pentaglutamate of LY23l5l4 is 100-fold more potent (Ki=3.4 nM), making LY231514 one of the most potent folate-based TS inhibitors[1].

In Vivo:The group of mice treated with PC61 plus Pemetrexed demonstrates statistically longer survival than other groups. In a survival analysis, significantly better survival is observed in the group of mice treated with PC61 plus Pemetrexed compare with those treated with PC61 alone, rat IgG plus Pemetrexed, or no treatment[2].

References:
[1]. Shih C, et al. LY231514, a pyrrolo[2,3-d]pyrimidine-based antifolate that inhibits multiple folate-requiring enzymes. Cancer Res. 1997 Mar 15;57(6):1116-23. [2]. Anraku M, et al. Synergistic antitumor effects of regulatory T cell blockade combined with pemetrexed in murine malignantmesothelioma. J Immunol. 2010 Jul 15;185(2):956-66.

[Association between the HER2 Gene Status and the Efficacy of First-line Pemetrexed Combined with Platinum Chemotherapy in Patients with Advanced Lung Adenocarcinoma].[Pubmed:30909992]

Zhongguo Fei Ai Za Zhi. 2019 Mar 20;22(3):137-142.

BACKGROUND: Human epidermal growth factor receptor 2 (HER2) is one of the driver genes of non-small cell lung cancer (NSCLC). Several studies have shown that the efficacy of Pemetrexed in HER2-mutant NSCLC is controversial. The aim of this study is to investigate the efficacy of Pemetrexed combined with platinum chemotherapy in patients with HER2-mutant and HER2 wild-type lung adenocarcinoma. METHODS: The clinical data of 106 cases of EGFR, ALK, ROS-1, KRAS, BRAF, RET and MET-negative patients with advanced lung adenocarcinoma patients who diagnosed by histopathology in the First Affiliated Hospital of Zhengzhou University were retrospectively reviewed. The relationships between HER2 gene status, clinical characteristics and response and progression-free survival (PFS) were analyzed. RESULTS: All of the 106 patients' HER2 status were determined. HER2 mutations occurred in 32 cases (30.2%), no mutations in 74 cases (69.8%). HER2 mutations were common in young, non-smoking and female patients. All patients received first-line Pemetrexed and platinum-based chemotherapy. The objective response rate (ORR) and disease control rate (DCR) of patients with HER2-mutant lung adenocarcinoma were significantly higher than those without HER2 mutations (40.6% vs 14.9%, chi(2)=8.464, P=0.004; 93.8% vs 68.9%, chi(2)=6.327, P=0.012), and the difference was statistically significant. According to univariate analysis, the PFS was significantly associated with the brain metastases, maintenance chemotherapy and HER2 gene status (P<0.05), but not with age, gender, smoking history, oligometastases, liver metastases and type of platinum (P>0.05). Cox multivariate analysis indicated that HER2 mutation was an independent positive prognostic factor of PFS (P=0.038). CONCLUSIONS: HER2-mutant lung adenocarcinoma patients with first-line Pemetrexed combined with platinum chemotherapy have greater clinical benefit than HER2 wild-type patients.

Pharmacokinetically-guided dosing of pemetrexed in a patient with renal impairment and a patient requiring hemodialysis.[Pubmed:30885337]

Lung Cancer. 2019 Apr;130:156-158.

OBJECTIVES: Pemetrexed is indicated for non-small cell lung cancer and mesothelioma. Dosing is based on body surface are (BSA), while renal function is the only determinant for exposure and thus toxicity. BSA-based dosing introduces large variability in exposure and may lead to (hemato)toxicity in patients with impaired renal function. Therefore, Pemetrexed is contraindicated in renal impairment. The presented cases provide proof-of-concept for pharmacokinetically-guided dosing of Pemetrexed in a haemodialysis patient and a patient with mild renal impairment. METHODS: The pharmacokinetic target was an area under the concentration-time curve (AUC) of 123-205 mg.h/L. Using a previously developed population pharmacokinetic model, individual pharmacokinetics were estimated. RESULTS: Both patients had an exposure above target after the initial dose, but a proportional dose reduction resulted in a therapeutic exposure in both patients (185 and 166 mg.h/L, respectively), that was well-tolerated. Interestingly, a threefold increase in systemic clearance of Pemetrexed was observed during hemodialysis (from 1.00 L/h to 3.01 L/h), which approximates the population clearance of Pemetrexed. CONCLUSION: Altogether, we showed that pharmacokinetically-guided dosing of Pemetrexed may be a feasible strategy for patients with lung cancer and renal impairment.

Clinical efficacy and safety evaluation of pemetrexed combined with radiotherapy in treatment of patients with lung adenocarcinoma brain metastasis.[Pubmed:30854063]

Oncol Lett. 2019 Mar;17(3):2874-2880.

Clinical efficacy and adverse reactions of Pemetrexed combined with stereotactic gamma-ray radiotherapy in the treatment of patients with lung adenocarcinoma brain metastasis in The First People's Hospital of Yunnan Province were evaluated. A total of 67 patients with lung adenocarcinoma brain metastasis in experimental group were treated with simple Pemetrexed chemotherapy, and then with radiotherapy, followed by Pemetrexed chemotherapy. Their treatment results were compared with those of 53 patients treated with simple gamma knife in control group. The results were analyzed by comparing the clinical efficacy, side reactions, serum level changes, and survival between the two groups. Among 67 patients in the experimental group, there were 16 cases of complete response (CR), 39 cases of partial response (PR), 7 cases of stable disease (SD) and 5 cases of progressive disease (PD), with an effective rate of 82.09% (55/67) and a tumor local control rate of 92.54% (62/67). Among 53 patients in the control group, there were 13 cases of CR, 20 cases of PR, 9 cases of SD and 11 cases of PD, with an effective rate of 62.26% (33/53) and a tumor local control rate of 79.25% (42/53). There were statistically significant differences in the effective rate and local control rate between the two groups (P<0.05). The 6-, 12- and 24-month survival rates in experimental group were higher than those in control group (P<0.05). The main adverse reactions after Pemetrexed combined with radiotherapy were lower than those after simple radiotherapy (P<0.05). The expression levels of the tumor markers carcinoembryonic antigen (CEA) and cytokeratin fragment antigen 21-1 (CYFRA21-1) in the two groups of patients after treatment were lower than those before treatment (P<0.05). After treatment, the expression levels of serum CEA and CYFRA21-1 in the experimental group were significantly lower than those in the control group (P<0.05). Pemetrexed combined with radiotherapy in the treatment of lung adenocarcinoma brain metastasis is more effective than simple radiotherapy, with lighter adverse reactions, worthy of clinical application and promotion.

Pemetrexed (LY231514) is a novel antifolate, the Ki values of the pentaglutamate of Pemetrexed (LY231514) are 1.3, 7.2, and 65 nM for inhibits thymidylate synthase (TS), dihydrofolate reductase (DHFR), and glycinamide ribonucleotide formyltransferase (GARFT), respectively.

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