Although survival outcomes have improved dramatically in pediatrics with acute lymphoblastic leukemia (ALL), cure rates for adult ALL patients have been estimated to be only 40% (1, 2). According to several studies, the initial response affects the prognosis of ALL. High levels of minimal residual disease (MRD) have been found to be associated with decreased relapse-free survival (RFS) after induction therapy. Thus, any potential factor that could affect the initial response of induction treatment needs to be reduced to maximize long-term responses. For newly diagnosed adult ALL patients, the regimen consisting of vincristine, prednisolone, daunorubicin, and L-asparaginase (VPDL) is used as induction therapy (3).

L-asparaginase (ASNase) is an enzyme that catalyzes the hydrolysis of L-asparagine into L-aspartic acid (Asp). In blood and cerebrospinal fluid, ASNase leads to a rapid lowering of the levels of asparagine, an amino acid that is crucial for cell growth (4–7). While normal cells can synthesize asparagine, leukemic lymphoblasts lack asparagine synthetase and are incapable of de novo asparagine synthesis, which makes them dependent on the exogenous supply of asparagine. ASNase results in apoptosis of tumor cells by draining all circulating asparagine as shown in Figure 1 (8). Previous binding and inhibition studies (9–11) demonstrated the interaction between this enzyme drug and its product, Asp. One study found that Asp competitively inhibits ASNase with the inhibition constant of 80 μM (9). Based on these studies, a way to chemically remove Asp from ASNase was suggested to maintain the activity of ASNase and to prevent this interaction. Now, commercially supplied ASNase does not contain Asp.

Meanwhile, ALL patients undergoing chemotherapy suffer from malnutrition due to mucositis and anorexia caused by chemotherapy, which contributes to the mortality rate of cancer patients (12–16, 26). Total parenteral nutrition (TPN) provides a way to deliver nutrients directly into the bloodstream to help maintain adequate nutrition in these patients, who may not be able to consume enough food orally. TPN products contain several kinds of amino acids, and Asp is included among them. Asparagine, on the other hand, is excluded from the TPN products because normal cells can synthesize asparagine via the actions of asparagine synthetase. Because Asp-containing TPN (Asp-TPN) formulations are being concomitantly used with ASNase, we are concerned that Asp in TPN may affect the clinical response of ASNase. However, whether the interaction between ASNase and Asp-TPN would impact the clinical outcomes in newly diagnosed ALL patients has never been studied. As previously mentioned, achieving complete remission (CR) with induction therapy is important for ALL prognosis. If an amino acid known to affect the activity of the cornerstone of induction therapy is being administered concurrently with TPN, clinical analysis of the interaction is significant. Accordingly, we compared the response, relapse, and safety between the control and Asp-TPN groups to ensure ASNase and TPN can be used concomitantly in ALL patients.

In this retrospective cohort study, the clinical effects of concomitant administration of Asp-TPN formulation and ASNase were evaluated for the first time. Overall, concurrent infusion of Asp-TPN with ASNase did not affect the response of the induction therapy or the very early relapse rate in patients with ALL.

It was imperative to investigate this topic for three primary reasons. To begin with, despite previous in vitro studies suggesting the interaction between ASNase and Asp, no study has evaluated whether Asp-TPN would clinically impact the effectiveness of ASNase or not in ALL patients. Furthermore, the new evidence was necessary to decide on the optimized TPN formulation that had minimal interactions with the chemotherapy in ALL patients. Since Asp plays a role in hormone production and release, and helps the nervous system function normally, it is contained in many commercial TPN formulations used for cancer patients. However, no evidence is available on the effectiveness of concomitant administration of Asp-TPN formulations for patients treated with ASNase. In this study, 82.5% of TPN users received Asp-containing formulations. All TPN formulations for patients were ordered by physicians without any preference, which minimize potential bias in the selection of TPN. By conducting this research, we aimed to provide evidence-based recommendations in selecting the appropriate TPN for patients undergoing induction therapy. To determine the optimal TPN formulation for patients receiving ASNase in clinical practice, further studies with larger sample sizes, longer follow-up periods, and well-defined prospective protocols are needed to validate the findings of this study. Moreover, evaluating any factors that would alter the effectiveness of the chemotherapy would help improve the survival rates of patients with ALL.

Our study showed that the concomitant use of ASNase and potential enzymatic inhibitor Asp-TPN formulation did not have an impact on the response and relapse rates of ASNase-including induction therapy, which is inconsistent with previous in vitro studies. Asp has been reported to competitively inhibit ASNase in the 6–50 μM range with an inhibition constant (K_i) of 80 μM (9, 19). The median plasma concentration of Asp in healthy adults was reported as 6 μM (20). Although limited studies on the changes in amino acid concentration after parenteral nutrition are available, a previous study (21) showed that Asp concentration rapidly increased to about 20 μM after TPN administration, a finding that shows the possibility of the interaction between TPN and ASNase. However, the level of enzyme inhibition may vary depending on several factors, such as metal ions, pH, and concentration of the substrates in the mixture, and these factors may be the reason the results of this study were different from those of in vitro studies. Additionally, for predicting inhibitory drug–drug interactions, it is necessary to consider the ratio of the concentration of the inhibitor to its inhibitory constant and the ratio of area under the curve (AUC) comprehensively (22). Although not presented in the current study, we also analyzed a dose-dependent relationship between the amount of Asp in the TPN and the response outcomes with no association between these two parameters. According to the results, the concomitant use of ASNase and Asp-TPN was associated with an increased risk of early relapse. However, the observed increase in risk was not statistically significant, with a p-value of 0.85. As very early relapse is critical for the prognosis of ALL, further studies considering comprehensive factors with the large number of populations are expected to clarify the relationship between the concomitant use of ASNase and Asp-TPN and the risk of early relapse of ALL.

In this study, we specifically evaluated LFT elevation, which is the most common toxicity of both TPN and ASNase. (23, 24). Although TPN causes a transient increase in aminotransferase concentrations during the first 1 to 3 weeks of TPN, patients receiving long-term TPN may develop TPN-induced liver disease as suggested in previous reports (22, 25). The median duration of TPN administration in our study was less than a week. Thus, this such short-term TPN use during 28-day VPDL induction therapy is unlikely to aggravate ASNase-associated hepatotoxicity. By comparing the frequency and severity of LFT elevation in both groups, we aimed to determine if combination treatment had a higher risk of liver toxicity. Monitoring other ASNase-induced complications such as pancreatitis and disseminated intravascular coagulation (DIC) is important in evaluating the safety of the treatment. However, due to the retrospective nature of the study, it was not possible to include these in the analysis, since triglycerides, or markers for other rare complications were not routinely checked unless patients showed signs or symptoms. A prospective study design with routine monitoring and systemic recording of these parameters would provide more comprehensive understanding of the safety profile. Nevertheless, this study is valuable as it represents an initial attempt for safety evaluation of Asp-TPN in ASNase-treated ALL patients.

Several study limitations should be discussed. First, a limited number of patients in each matched cohort was found as the study was conducted in a single center. According to the latest national cancer statistics in Korea, ALL is a rare disease as it comprises only 1.5% of the total number of new cancer cases. Another reason for the limited number of patients is due to matching process, which enabled the research to minimize the selection bias. Furthermore, due to its retrospective nature, the study had a lack of information on concentrations of amino acid and activity of ASNase in the body that could support our findings. Moreover, gathering information on the amount of dietary intake was limited, but all patients received a low-bacteria diet provided by the hospital. Not all patients in the control group received TPN. However, the authors tried to control the potential bias by propensity score matching including factors that could affect the nutrition status. Also, most of the reason to initiate TPN therapy was to prevent mild, rather than severe, malnutrition caused by mucositis. Additionally, as pediatric patients have distinctive pharmacokinetics and pharmacodynamics, extrapolating the findings from adult patients to pediatric population should be careful. ALL is the most common malignancy in pediatric patients. Therefore, further studies specifically designed for pediatric population is needed in the future.

This study is the first that evaluates the clinical outcomes of the concomitant use of ASNase and Asp-TPN formulations. There were no differences in response rates and relapse-free survival between Asp-TPN and control groups. Peak levels of LFTs and the frequency of LFTs increases were also similar. Based on the results of the current study, Asp-TPN can be administered without concern in ALL patients receiving ASNase as induction therapy.

The datasets generated during and/or analysed during the current study are available from the corresponding author on reasonable request. Requests to access these datasets should be directed to JO, jmoh@snu.ac.kr.

The studies involving human participants were reviewed and approved by Seoul National University Hospital Institutional Review Board. Written informed consent for participation was not required for this study in accordance with the national legislation and the institutional requirements.

KoM: conceptualization, methodology, investigation, formal analysis, writing—original draft, writing—editing, and visualization. KimMG: conceptualization, methodology, and writing—review & editing. YoonS-S, SuhSY, and ChoY-S: resources. KimI-W: methodology and writing—review & editing. OhJM: methodology, resources, writing—review & editing, supervision, and project administration. All authors contributed to the article and approved the submitted version.

This study was supported by the National Research Foundation of Korea grant funded by the Korea government (MSIT) (no. 2021R1A2C1006046).

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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