Comparison of elapegademase and pegademase in ADA-deficient patients and mice

Abstract

The absence of adenosine deaminase (ADA) causes severe combined immune deficiency (SCID), which has been treated with PEGylated bovine-extracted ADA (ADAGEN). ADAGEN was recently replaced by a PEGylated recombinant bovine ADA, expressed in Escherichia coli (elapegademase, ELA-ADA). Limited information on ELA-ADA is available. ADA enzymatic activity of ELA-ADA and ADAGEN was assessed in vitro at diverse dilutions. ADA activity and immune reconstitution in an ADA-SCID patient treated with ELA-ADA were compared with age-matched patients previously treated with ADAGEN. ADA activity and thymus reconstitution were evaluated in ADA-deficient mice following ELA-ADA or ADAGEN administered from 7 days postpartum. In vitro, ADA activity of ELA-ADA and ADAGEN were similar at all dilutions. In an ADA-SCID patient, ELA-ADA treatment led to a marked increase in trough plasma ADA activity, which was 20% higher than in a patient previously treated with ADAGEN. A marked increase in T cell numbers and generation of naive T cells was evident following 3 months of ELA-ADA treatment, while T cell numbers increased following 4 months in 3 patients previously treated with ADAGEN. T cell proliferations stimulation normalized and thymus shadow became evident following ELA-ADA treatment. ADA activity was significantly increased in the blood of ADA-deficient mice following ELA-ADA compared to ADAGEN, while both treatments improved the mice weights, the weight, number of cells in their thymus and thymocyte subpopulations. ELA-ADA has similar in- vitro and possibly better in-vivo activity than ADAGEN. Future studies will determine whether ELA-ADA results in improved long-term immune reconstitution.

Keywords: adenosine deaminase deficiency; elapegademase; enzyme replacement therapy; pegademase; severe combined immunodeficiency.

Figure 1

Elapegademase and pegademase enzyme activity in vitro. Activity of 4 µl elapegademase (ELA–ADA) and pegademase (ADAGEN) serially diluted in phosphate‐buffered saline (PBS) was determined by the percentage of 1 µmol [8‐14C]adenosine converted during 30 min. Results are the mean ± standard deviation of three independent experiments using three vials of each product.

Figure 2

Thymus recovery in an adenosine deaminase–severe combined immune deficiency (ADA–SCID) patient following elapegademase treatment. Thymus silhouette (arrows) in an ADA–SCID patient following 6 months of twice‐weekly elapegademase enzyme replacement therapy (ERT).

Figure 3

Elapegademase and pegademase effects on immune reconstitution in adenosine deaminase–severe combined immune deficiency (ADA–SCID) patients. The number of lymphocyte subpopulations, assessed by flow cytometry at the indicated time [months after initiation of enzyme replacement therapy (ERT)] in a patient receiving elapegademase (ELA–ADA, solid line) and three patients receiving pegademase (ADAGEN, dashed lines). (a) CD19⁺ B cells; (b) CD3⁻16⁺56⁺ natural killer (NK) cells; (c) CD3⁺CD4⁺ T cells; (d) CD3⁺CD8⁺ T cells.

Figure 4

Elapegademase and pegademase enzyme activity in adenosine deaminase (ADA)‐deficient mice. (a) ADA‐deficient [knock‐out (KO)] mice received 0·25 ml//kg body weight pegademase (ADAGEN, 62·5 units/kg) or elapegademase (ELA–ADA, 0·4 mg/kg) at 7 days postpartum. ADA activity (conversion of [8‐14C]adenosine to hypoxanthine) in the blood was determined at the indicated hours after treatment; n = 6 mice in each group from two independent experiments. Results are the mean ± standard deviation. *P = 0·02. (b) ADA‐deficient (KO) mice received 0·25 ml//kg body weight pegademase (ADAGEN, 62·5 units/kg) or elapegademase (ELA–ADA, 0·4 mg/kg) at 7, 10 and 13 days postpartum. ADA activity (conversion of [8‐14C]adenosine to hypoxanthine) in the blood was measured at the indicated hours after the third injection. Hatched area represents ADA activity in ADA^+/− and ADA^+/+ mice littermates, n = 6–9 mice in each group from two independent experiments. Results are the mean ± standard deviation. *P < 0·01, **P < 0·001 between ADA‐KO mice treated with ELA–ADA or ADAGEN.

Figure 5

Elapegademase and pegademase effects on the weight and thymus of adenosine deaminase (ADA)‐deficient mice. ADA‐deficient [knock‐out (KO)] mice received 0·25 ml//kg body weight pegademase (ADAGEN, 62·5 units/kg) or elapegademase (ELA–ADA, 0·4 mg/kg) at 7, 10 and 13 days postpartum. Treated and non‐treated ADA‐KO as well as normal littermate mice were assessed at 17–19 days postpartum. Results are the mean ± standard deviation with n = 3–6 in all groups. (a) Thymus weights; (b) number of thymocytes; (c) thymocyte subpopulation CD4⁻CD8⁻, CD4⁺CD8⁺, CD4⁺CD8⁻ and CD4⁻CD8⁺ assessed by flow cytometry; (d) body weights. *P < 0·01, ** P < 0·001 compared to untreated ADA‐KO mice.