Recombinant α1-Microglobulin (rA1M) Protects against Hematopoietic and Renal Toxicity, Alone and in Combination with Amino Acids, in a 177Lu-DOTATATE Mouse Radiation Model

Abstract

¹⁷⁷Lu-DOTATATE peptide receptor radionuclide therapy (PRRT) is used clinically to treat metastasized or unresectable neuroendocrine tumors (NETs). Although ¹⁷⁷Lu-DOTATATE is mostly well tolerated in patients, bone marrow suppression and long-term renal toxicity are still side effects that should be considered. Amino acids are often used to minimize renal radiotoxicity, however, they are associated with nausea and vomiting in patients. α₁-microglobulin (A1M) is an antioxidant with heme- and radical-scavenging abilities. A recombinant form (rA1M) has previously been shown to be renoprotective in preclinical models, including in PRRT-induced kidney damage. Here, we further investigated rA1M's renal protective effect in a mouse ¹⁷⁷Lu-DOTATATE model in terms of administration route and dosing regimen and as a combined therapy with amino acids (Vamin). Moreover, we investigated the protective effect of rA1M on peripheral blood and bone marrow cells, as well as circulatory biomarkers. Intravenous (i.v.) administration of rA1M reduced albuminuria levels and circulatory levels of the oxidative stress-related protein fibroblast growth factor-21 (FGF-21). Dual injections of rA1M (i.e., at 0 and 24 h post-¹⁷⁷Lu-DOTATATE administration) preserved bone marrow cellularity and peripheral blood reticulocytes. Administration of Vamin, alone or in combination with rA1M, did not show any protection of bone marrow cellularity or peripheral reticulocytes. In conclusion, this study suggests that rA1M, administered i.v. for two consecutive days in conjunction with ¹⁷⁷Lu-DOTATATE, may reduce hematopoietic and kidney toxicity during PRRT with ¹⁷⁷Lu-DOTATATE.

Keywords: amino acids; bone marrow toxicity; oxidative stress; peptide receptor radionuclide therapy; radiation; renal damage; α1-microglobulin.

Figure 5

Impact of amino acid administration on the protective effects of rA1M. Urine albumin levels, corrected for creatinine (A), circulatory reticulocytes (B), and bone marrow cellularity (C) were measured 4 days after dosing in animals receiving NaCl and vehicle (volume corresponding to that of 150 MBq ¹⁷⁷Lu-DOTATATE or rA1M injections, respectively), 150 MBq ¹⁷⁷Lu-DOTATATE with the vehicle (volume corresponding to that of rA1M injections), the vehicle (volume corresponding to that of rA1M injections) and Vamin (35 mg/200 μL, administered i.p.), rA1M (2 × 5 mg/kg) or Vamin (35 mg/200 μL, administered i.p.), and rA1M (2 × 5 mg/kg). Data is presented as scatter plots with mean ± SEM. Statistical comparison between groups was made with one-way ANOVA with a Šídák’s multiple comparisons post hoc test. Comparison was made between ¹⁷⁷Lu-DOTATATE + vehicle and all groups, and between ¹⁷⁷Lu-DOTATATE + Vamin and rA1M with or without Vamin and between rA1M alone or rA1M + Vamin. Only significant differences are presented in the figure. ** p < 0.01, *** p < 0.001, **** p < 0.0001.

Figure 1

Pharmacokinetic study of rA1M. Plasma concentration of rA1M in female BALB/cJBomTac mice (n = 3–4/timepoint) after s.c. (20 mg/kg, (A)), i.v. (5 mg/kg, (B)), or i.p. (20 mg/kg, (C)) administration. In (D) all three administration routes are presented. Data is presented as mean ± SEM.

Figure 2

Evaluation of the protective effects of i.v. vs. s.c. administered rA1M. Albumin levels in urine (A) and plasma FGF-21 (B) were measured 4 days after dosing in animals receiving NaCl and the vehicle (i.v. or s.c., volume corresponding to that of 150 MBq ¹⁷⁷Lu-DOTATATE or rA1M injections, respectively), 150 MBq ¹⁷⁷Lu-DOTATATE with vehicle (i.v. or s.c., volume corresponding to that of rA1M injections), or with rA1M (i.v., 5 mg/kg or s.c., 20 mg/mg). Data is presented as scatter plots with mean ± SEM. Statistical comparison between groups was made with one-way ANOVA with a Šídák’s multiple comparisons post-hoc test. Comparison was made between groups with the same administration route and between rA1M i.v. and s.c. Only significant differences are presented in the figure. * p < 0.05, ** p < 0.01.

Figure 3

Evaluation of protective effect of different dosing regimen of rA1M. Urine albumin levels, corrected for creatinine (A), circulatory reticulocytes (B), representative image of bone marrow isolated single cells, showing red pellet as an effect of the irradiation treatment on depletion of white marrow (C), and bone marrow cellularity (D) were measured 4 days after dosing in animals receiving NaCl and the vehicle (volume corresponding to that of 150 MBq ¹⁷⁷Lu-DOTATATE or one dose of rA1M injection), 150 MBq ¹⁷⁷Lu-DOTATATE with vehicle (volume corresponding to that of one dose of rA1M injection), or with rA1M (1, 5 or 2 × 5 mg/kg). The representative gating strategies for flowcytometric evaluation are presented in Supplementary Figure S3. Data is presented as scatter plots with mean ± SEM. Statistical comparison between groups was made with one-way ANOVA with a Šídák’s multiple comparisons post hoc test. Comparison was made between ¹⁷⁷Lu-DOTATATE + vehicle and all groups in addition to between the different doses of rA1M. Only significant differences are presented in the figure. * p < 0.05, ** p < 0.01, *** p < 0.001, **** p < 0.0001.

Figure 4

Impact of amino acid co-administration on rA1M biodistribution. Animals were injected with ¹²⁵I-labelled rA1M alone (n = 8), or in combination with amino acids (Vamin, n = 8). Four (4) animals from each group were sacrificed after 10 (A) or 60 min (B). Organ specific uptake values were calculated as percent injected activity per gram tissue (%IA/g) in kidney, liver, spleen, and femur. Data is presented in bar graphs with mean ± SEM. No statistical differences between the two groups were detected following comparison between groups with a two-way ANOVA.