In this trial there were no DLTs associated with the administration of Huachansu, though we gave doses considerably higher than the conventional doses used in China (conventional doses = 20-25 mL; our highest dose = 162 mL). The grade I and II side effects that may have been related to Huachansu observed in this study were hematologic, gastrointestinal, mucocutaneous, and cardiovascular in nature (see ). These side effects did not appear dose related, and it was unclear for many of them whether they were genuinely related to drug or rather to the underlying disease. Eleven patients (73%) had no toxicities greater than grade I. Importantly, significant cardiac toxicity was not observed despite the administration of high doses of this cardiac glycoside-containing compound. There were also no statistically significant changes in cancer-related symptoms associated with the administration of Huachansu. The dose was not escalated beyond level 5 (i.e., 90 mL/m2
, for a total of 162 mL), even though no DLT’s were detected at this high dose, as this was already approximately eight times the dose generally used in China (20-25 ml) and because of the observation of stable disease at the low doses that are comparable to the dose commonly used.14
Although there were no complete or partial responses in this study, some patients had stable disease (6 of 15 patients with a median duration of 6 months [range, 3.5 to 11.1 months]). Of particular note, 1 patient with hepatocellular carcinoma had a 20% reduction in tumor mass that lasted for more than 11 months.
Several studies have suggested the potential therapeutical value of cardiac glycosides such as digoxin, oleandrin, and bufalin in the treatment of various cancers.15-21
Bufadienolides (cardiac glycosides derived from Chansu), including bufalin, cinobufagin, and epoxybufanolides, have been found to inhibit tumor cell proliferation and induce apoptosis in human leukemia HL-60 and U937 cells, prostate cancer PC3 and DU145 cells, and human epidemoid carcinoma KB cells.12, 13, 21, 22
These glycosides induce differentiation and apoptosis in a broad range of human leukemia cell lines through alteration of expression of c-myc and bcl-2. Additionally, it was found that bufalin inhibited proliferation of human leukemia U927 cells by the activation of mitogen-activated protein kinase (MAPK) via a signaling pathway that included Ras, Raf-1, and MAPK kinase-1.23
Furthermore, research suggests that bufalin induces cell cycle changes in human leukemia cells by reducting levels of topoisomerase II.13, 22
Studies conducted in China have suggested that Huachansu can inhibit tumor cell growth and improve immunologic function.24
Indeed, in vitro
experiments showed that Huachansu suppressed the growth of various human cancer cell lines 25, 26
and inhibited the proliferation of MGC-80-3 and SMMC-7721 cells by causing S phase cell cycle arrest and inhibiting Bcl-2 expression.27
In addition, we previously found that the proliferation of human melanoma BRO cells was inhibited by Huachansu via G2/M cell cycle arrest (unpublished observations, P. Yang). This anticancer activity might be associated with activation of the MAPK pathway, as evidenced by increased pERK in BRO cells (unpublished observations, P. Yang), suggesting that cardiac glycosides at least partially contribute to the anticancer activity of Huachansu.11
The same product that was used in the in vitro
work was used in this trial. Furthermore, Huachansu has previously been found to markedly inhibit the biosynthesis of DNA and RNA in H22 AH, ascites hepatoma cells 28
and was also effective in reducing tumor volume and increasing survival in mice bearing Lewis lung tumor cells.29
Therefore, Huachansu appears to have important antineoplastic properties that warrant further clinical testing.
We were not able to conduct formal pharmacokinetic analyses in this trial in largely because Huachansu is not a conventional drug. Rather, it is a complex extract containing multiple chemical components. There are few biomarkers or specific chemical constituents that could be used to assess pharmacokinetic parameters, and our preclinical research suggests that the antitumor activity of Huachansu can be attributed to multiple components of the extract and not a single active principal ingredient. This is one of the challenges of researching natural products. Despite these challenges, it should be noted that the product has a uniform manufacturing process and three different lots tested had virtually identical proportion of bufalin and fingerprints. We were able to measure, in a limited fashion, plasma concentrations of bufalin, a known cardiac glycoside that has been reported to have anticancer activity against multiple cancer cell lines.12, 13, 21, 22
Bufalin was not detected in the plasma of patients who received level 1 and 2 doses probably because of the relatively low level of bufalin in the Huachansu injection and a minimum the detection level of 0.15 ng/mL using our assay. Regardless, we were at least able to quantify the bufalin levels in the patients who received dose levels 3-5. There was a dose-dependent increase in bufalin levels, with maximum levels of bufalin reached 2 hours after the infusion and no suggestion of accumulation of the drug in plasma, which may be due to the drug’s short half-life. Given that the patient with stable disease and 20% tumor shrinkage was treated with the level 1 dose, there was no clear correlation between the plasma bufalin content and antitumor effect of Huachansu. However, the small number of patients precluded making an association between dose and response. A phase II clinical trial of Huachansu is currently ongoing at the Fudan University Cancer Hospital for patients with advanced pancreatic cancer. This is part of the International Center of Traditional Chinese Medicine for Cancer funded by the NCI. Patients are randomized and treated with gemcitabine and Huachansu (20 mL/m2
) or gemcitabine and placebo. The 20mL/m2
dose of Huachansu in that trial was chosen based on historical use and on our finding of the best response at the lower doses in the current trial. We conclude the Huachansu is well tolerated, even at doses eight times those normally administered in China, and that, as a single agent, it can result in disease stabilization in a subset of patients.