Range of Neurological Signs in Cynomolgus Monkeys After Intrathecal Bolus Administration of Antisense Oligonucleotides

Abstract

Intrathecal (IT) dosing (ie, injection into the subarachnoidal space at the lumbar region) is a common route of administration in cynomolgus monkey preclinical safety studies conducted for antisense oligonucleotides (ASO) that target central nervous system diseases. Herein we report on neurological signs that have been observed in 28 IT studies conducted in 1,016 cynomolgus monkeys. Neurological signs were classified into 5 groups: (1) A nonadverse transient absence of lower spinal reflexes. This observation occurred at low incidence in nontreated animals and in those that were injected artificial cerebrospinal fluid. The incidence increased in animals that were injected an ASO. Reflexes were present again at 24 hours or 48 hours after dosing. The incidence appeared to increase with dose. (2) Test-article-related adverse muscle tremor or muscle spasticity occurring during the injection procedure or immediately thereafter. In one-third of animals this finding responded to treatment with diazepam, in two-third it required euthanasia. (3) Neurological findings occurring between 30 minutes and 4 hours after dosing were characterized by any combination of ataxia, paresis, nystagmus, urinary incontinence, or muscle tremor. Those conditions either spontaneously resolved or they slowly worsened, eventually resulting in a poor general condition. (4) Neurological findings due to spinal cord injury were characterized by rapidly progressing paralysis of hind limbs. Magnetic resonance imaging revealed a focal hyperintense lesion, indicative of spinal cord necrosis. (5) Test-article-related adverse hind limb paresis or paralysis that occurred between 2 and 18 days after dosing. Those findings were rare and resulted in a poor general condition requiring euthanasia.

Angelman syndrome patient neuron screen identifies a potent and selective clinical ASO targeting UBE3A-ATS with long lasting effect in cynomolgus monkey

“…These changes correlated with transient neurological observations noted at 2 and/or 6 hrs post dose which included decreased proprioceptive hindlimb positioning, decreased or absent tactile and/or visual hindlimb placing reaction, decreased or absent hindlimb flexor reflex and/or decreased muscle tone (data not shown). These types of reactions are rather typical for intrathecally dosed ASOs and are generally not adverse ( 24 ). In terms of histopathological analysis, test item related findings of neuronal vacuolation in the nervous system, vacuolated macrophages in spinal cord, injection site and lymph nodes, and basophilic granules in the kidneys were not considered adverse based on their low severity and lack of associated degenerative/inflammatory changes or clinical pathological changes (assessing renal function).…”

Safe and Effective Cynomolgus Monkey GLP—Tox Study with Repetitive Intrathecal Application of a TGFBR2 Targeting LNA-Gapmer Antisense Oligonucleotide as Treatment Candidate for Neurodegenerative Disorders

“…These transient changes in spinal reflexes were considered non-adverse and represented an oligonucleotide class-specific finding after i.th. administration [44]. A recently published paper by Korte et al described these effects as not necessarily ASO-related, since they also occurred in aCSF-treated animals, indicating the dosing procedure per se influences neurological parameters [45].…”

“…A recently published paper by Korte et al described these effects as not necessarily ASO-related, since they also occurred in aCSF-treated animals, indicating the dosing procedure per se influences neurological parameters [45]. Further, persistent loss of one or more reflexes was described as non-adverse, since no fundamental physiological deficit or behavioral alterations were noted [44]. Following 13 weeks of intrathecal NVP-13 treatment, mononuclear cell infiltrates in the nervous system were considered to have resulted from proinflammatory effects of ASOs.…”

Progress report on new antiepileptic drugs: A summary of the Sixteenth Eilat Conference on New Antiepileptic Drugs and Devices (EILAT XVI): II. Drugs in more advanced clinical development

“…Preclinical toxicology findings were consistent with those observed with intrathecal administration of other oligonucleotides. 97 In non-Good Laboratory Practice studies in nonhuman primates, at levels above the NOAEL, hind limb paresis was observed. At extremely high dose levels, acute convulsions were observed.…”