FIGURE 1 Activity analysis of 0.05, 0.5 and 5.0 IU/mL of
commercial L-ASNases distributed in Colombia on B-ALL cells incubated
for 24 (Red Circle), 48 (Green Square) and 72 (Blue Triangle) hours.
Abbreviations: L-ASNase, L-asparaginase; NC, Negative Control.
Statistical differences (p <0.001) were identified
between ASA2-4 activity and negative control just at 5.0 UI/mL with 72
hours of incubation (Fig. 1C) , which is a condition used in
research exclusively8. ASA5 induced apoptosis at
>90% of cells at 72 hours of incubation using the half of
therapeutic dose concentration (0.05 UI/mL) (Fig. 1A) and ASA1
reached this percentage at the same time of incubation using 10 times
more concentration (0.5 UI/mL) (Fig. 1B) . ASA6 induced
statistically significant higher lethality of cells compared to ASA2-4
and the negative control (p <0.001), however 28.9% of
cell were still viable after 72 hours with 5.0 UI/mL of this enzyme(Fig. 1C) .
DISCUSSION
Unlike normal cells, leukemic cells lack partially or totally of
asparagine synthase activity , so they depend on importing asparagine
from the extracellular medium for their proteins
syntehsis9. Thus, a depletion of asparagine in
extracellular medium by L-ASNase enzyme affect selectively tumoral
cells. This is the reason for its use for more than 60 years ago to
treat patients with ALL and lymphoma until today10.
Unfortunately, some patients have important allergic reactions to
L-ASNase enzyme due to their bacterial origin and it is necessary to
change the formulation11. Diverse sources of microbial
L-ASNase have been implemented and currently three are commercially
available to treat patients (Native E. coli L-ASNases,E. coli PEG-asparaginase,
and E. chrysanthemi L-ASNases)12. Although they
all have advantages and disadvantages, their election is based on the
immunological response of patients and the availability to the health
system in each country, because there is no significant differences on
patients outcome13.
Nevertheless, developing countries have difficulties to acquire E.
coli PEG-asparaginase and E. chrysanthemi L-ASNases because of
their higher commercial prices. Here, biogeneric formulations take an
important role to provide all children and adolescents with cancer a
better chance of cure, described in the WHO Global Initiative for
Childhood Cancer. However, there are some concerns about the quality of
this drugs and our results support those worries.
Based on our results, we conclude that there are differences between the
formulations of L-ASNase distributed in Colombia, which raises concerns
about the quality of the treatment administered to patients. These
differences may explain the limited ability of some formulations to
achieve therapeutic levels in patient serum reported by groups from
India and Brazil3–6.
Inadequate transport and storage conditions, failures on reconstitution
protocol, use of medicaments out of expiration date, defective reagent
lot, unreported excipients, and low quality at industrial production are
factors that can affect the performance of medications. Some of these
factors were standardized previous to our analysis, but other factors
cannot be controlled for the laboratory or health care facilities.
Consequently, we present a preclinical protocol that can be implemented
to evaluate the quality of L-ASNase formulations. This methodology can
analyze the activity of every batch of L-ASNase, which will allow for
optimal regulation by the competent national entities, screening
L-ASNase activity before being marketed and administered to patients
with ALL. Thus, we present a methodology that should be included as a
regulatory protocol for these drugs, which allow access to effective
therapies while protecting the safety of patients.