Cancer:
Leukemia, AML, CML, myelodysplastic syndrome (MDS)
Action: Induces apoptosis, anti-tumor activity
Homoharringtonine (also known as Omacetaxine mepesuccinate) is isolated from Cephalotaxus harringtonia (K.Koch).
Homoharringtonine/omacetaxine is a unique agent with a long history of research development. It has been recently approved by the Food and Drug Administration for the treatment of chronic myeloid leukemia after failure of 2 or more tyrosine kinase inhibitors. Research with this agent has spanned over 40 years (Kantarjian, O'Brien, & Cortes, 2013).
Leukemia
Homoharringtonine (HHT), first isolated from the Chinese evergreen Cephalotaxus harringtonia, has been demonstrated to have a broad anti-tumor activity in rodents and anti-leukemic effects in humans. It was found that HHT was metabolized to an acid product [HHT acid; 2'hydroxy2' (acetic acid) 6'hydroxy6'methylheptanoyl cephalotaxine] when incubated with either human plasma or mouse plasma in vitro. The HHT concentration inhibiting 50% of the growth of human leukemic HL60 cells was 20 ng/ml, while for HHT acid it was 14,500 ng/ml, indicating that the acid form was more than 700 times less cytotoxic than HHT. The lethal dose of HHT affecting 50%(LD50) of mice was 6.7 mg/kg, but HHT acid produced no apparent toxic effects at doses up to 280 mg/kg (Ni et al., 2003).
Acute Myeloid Leukemia (AML)
The response to remission induction in elderly patients with acute myeloid leukemia (AML) remains poor. Patients were treated with the HA regimen consisting of homoharringtonine (2 mg/m2/day for 7 days) and cytarabine (Ara-C, 100 mg/m2/day for 7 days). The overall response rate was 56.5% with complete remission (CR) rate of 39.1% and partial remission of 17.4%.
There was no early death in this cohort of patients. The estimated median overall survival (OS) time of all patients was (12.0 ± 3.0) months. The estimated OS time of the CR patients was 15 months. The estimated one-year OS rate of all patients treated with HA protocol was (49.3 ± 13.5) %. The estimated one-year OS rate of the CR patients was (62.5 ± 17.1) % (Wang et al., 2009).
Leukemia; Telomerase
The effect of HHT on the telomerase activity and apoptosis of human leukemia HL-60 cells was investigated. Telomerase activity of HL-60 cells was examined by the telomeric repeat amplification protocol (TRAP)–an enzyme-linked immunosorbent assay (ELISA). Apoptosis was analyzed by morphological observation, DNA agarose gel electrophoresis, flow cytometry (FCM), and TdT-mediated dUTP-biotin nick end labeling (TUNEL).
After treatment with HHT at 5-500 microg/l for 48 hours, the level of telomerase activity in HL-60 cells decreased in a dose-and time-dependent manner. Simultaneously, HL-60 cells underwent apoptosis. In conclusion, these data suggest that HHT can inhibit the telomerase content of HL- 60 cells effectively and induce apoptosis (Xie et al., 2006).
Chronic Myeloid Leukemia (CML)
Evidence confirmed HHT as an apoptosis inducer in tumor cell lines and fresh cells from cancer patients. The CR rate reported with HHT-based regimen in acute nonlymphocytic leukemia showed no statistical differences from that with DNR-based regimen, although the case number was limited.
Although with anti-growth activity in vitro and laudable achievement in acute and chronic myeloid leukemia treatment, the drug shows no beneficial effect in lymphocytic leukemia and solid tumors. The underlying mechanism for the discrepancy of efficacy remains unknown, and is a subject for further research (Luo et al., 2004).
Myelodysplastic Syndrome (MDS)
Homoharringtonine might have clinical activity in some patients with myelodysplastic syndrome (MDS) (Daver et al., 2013).
References