The observed incidence of anti-drug antibodies (ADAs) is highly dependent on the sensitivity and specificity of the assay. Differences in assay methods preclude meaningful comparisons of the incidence of ADAs in the trials described below with the incidence of ADA in other studies, including those of LOARGYS or of other pegzilarginase products.
The incidence of ADAs (i.e., anti-pegzilarginase-nbln antibodies and/or anti-PEG antibodies) in LOARGYS-treated pediatric and adult patients with ARG1-D over 6 to 274 weeks in Trials 1, 2, and 3 is summarized in Table 3.
- In Trial 2, anti-PEG antibodies were observed after the second LOARGYS dose and peak anti-PEG antibody titers occurred at Week 3. In Trial 1, peak anti-PEG antibody titers were observed at Week 7.
- Anti-pegzilarginase-nbln antibodies showed similar titer profiles as anti-PEG antibodies in Trial 2, while no obvious peak titer was observed in Trial 1.
- The anti-pegzilarginase-nbln antibody and anti-PEG antibody titers decreased during continued LOARGYS treatment with the median duration of ADA positivity lasting approximately two weeks.
The incidence of neutralizing ADA has not been characterized; however, it cannot be excluded that the ADAs that showed an effect on pharmacokinetics or pharmacodynamics of pegzilarginase-nbln had neutralizing activity.
Table 3: Incidence of ADAs in LOARGYS-Treated Pediatric and Adult Patients with ARG1-D (Trials 1, 2, and 3)1
| 1 ADA incidences are rounded up to the nearest integer. |
| Trial 1 (up to 152 weeks) (N= 32) | Trials 2 and 3 (up to 274 weeks) (N= 16) |
ADA incidence | 13% | 50% |
Both anti-pegzilarginase-nbln antibodies and anti-PEG antibodies | 3% | 31% |
Only anti-pegzilarginase-nbln antibodies | 9% | 6% |
Only anti-PEG antibodies | 0% | 13% |
Anti-Drug Antibody Effects on Pharmacokinetics
In Trial 1, pharmacokinetic (PK) samples evaluable for the impact of ADA were available in 2 LOARGYS-treated patients. These 2 patients had pegzilarginase-nbln AUC that were comparable to pegzilarginase-nbln AUC in patients who did not develop anti-pegzilarginase-nbln antibodies.
Across Trials 1, 2, and 3, LOARGYS-treated patients who had higher anti-PEG antibody titers had lower pegzilarginase-nbln AUC compared to those with lower anti-PEG antibody titers or those who did not develop ADA.
Anti-Drug Antibody Effects on Pharmacodynamics
In Trial 1, pharmacodynamic (PD) samples evaluable for the impact of anti-pegzilarginase-nbln antibodies were available in 2 LOARGYS-treated patients. These 2 patients had similar plasma arginine levels to patients who did not develop anti-pegzilarginase-nbln antibodies at the same dosage.
Across Trials 1, 2, and 3, LOARGYS-treated patients who had higher anti-PEG antibody titers had lower plasma arginine reduction compared to those who did not develop anti-PEG antibodies and those with lower anti-PEG antibody titers.
In the LOARGYS-treated patients who exhibited the highest anti-pegzilarginase-nbln antibody titers and the highest anti-PEG antibody titers, the arginine concentrations were higher after the ADAs developed.
Anti-Drug Antibody Effects on Safety and Efficacy
Hypersensitivity reactions occurred at a higher incidence in LOARGYS-treated patients who were ADA-positive compared to those who were ADA-negative [see Adverse Reactions (6.1)]. Across Trials 1, 2, and 3, of the 4 LOARGYS-treated patients who experienced hypersensitivity reactions and had an evaluation of anti-pegzilarginase-nbln IgE antibodies, 25% (1/4) of patients had positive results for anti-pegzilarginase-nbln IgE antibodies.
No clinically significant effect of ADAs on the incidence of injection site reactions was identified over the LOARGYS treatment duration of 274 weeks.
The effect of ADAs on the effectiveness of LOARGYS in the treatment of hyperargininemia in adult and pediatric patients 2 years of age and older with ARG1-D is unknown.