Which risks did regulators probe for approved oligonucleotides?

“Activation of complement, dose-related in magnitude, was observed in all SRP-4045 dose groups, as evidenced by increases in Bb and C3a.”

“Protein binding was low (<37%) in animal and human plasma, and there was extensive tissue distribution, with highest and lowest levels of radioactivity in kidney and brain, respectively”

“Vutrisiran did not stimulate various cytokines in human whole blood samples in vitro and in a 13 weeks DRF toxicity study in monkeys in vivo.”

“Based on the QWBA data, radioactivity in tissues generally peaked by 48 hours postdose, and was highest in liver, lymph nodes, kidneys, and thoracic ducts.”

“A potential test article-related minimal increase in mean complement Bb levels was observed at 4 hours post-dose on Day 1 in animals at 30 mg/kg/week.”

“the highest concentrations of radioactivity were observed in the liver and kidney, at their tmax observed at 24- and 168-h post dose in the liver and kidney, respectively.”

“No drug-related effects were observed on TDAR, immunophenotyping, physical development, neurobehavioral development, or on the male reproductive system.”

“Widespread tissue distribution was detected by QWBA, with highest peak levels in kidney (165000 ng-eq/g). At 56 days postdose, radioactivity was detected only in kidney and urine.”

“All samples in the rat were negative. In the monkey study one sample was positive at 30 mg/kg/week (on day 169) and 3 samples were positive at 100 mg/kg/week, all from one animal (on days 85, 169 and 253).”

“Quantitative whole-body autoradiography confirmed that givosiran is distributed to a limited number of tissues, with high exposures observed in the liver, kidneys, kidney cortex, and lymph nodes.”

“Therefore, it seems that the main adverse reaction due to an exaggerated pharmacological effect of complement inhibition is an increased susceptibility to infections.”

“An ocular tissue distribution study was conducted in male Dutch-Belted rabbits following a single IVT injection of avacincaptad pegol (3 mg/eye) to both eyes”

“Complement activation was apparent in monkeys at SC doses of > 20 mg/kg (~7x clinical exposure) and at intravenous (IV) doses as low as 12 mg/kg, as evidenced by transient rises in the level of the complement factor B split product, Bb, and the depletion of complement factor C3 with repeated dosing.”

“The organs showing the highest tissue levels in all species are kidney, liver, spleen, lymph nodes and bone marrow, with the kidney and liver showing the highest concentrations. Little to no drug distributes to skeletal muscle, eye or the brain.”

“In a 40-week toxicity study in NHPs, delayed or suppressed IgM (data not shown) and IgG (see Figure 1, below) responses were observed across the dose range at ≥ 2 times the clinical MRHD (BSA) (≥ 30 mg/kg Q4W) in response to keyhole limpet hemocyanin (KLH) sheep antigen”

“In rats, inclisiran-associated radioactivity widely distributed to most tissues with the highest concentrations (based on Cmax) observed at the subcutaneous dose site, and in the liver (target organ), and kidney cortex (site of elimination).”

“Overall, there were no indications that pegaptanib induced a local or systemic immune response and there were only minor effects on immune cells and organs at high exposures.”

“After IVT administration, radioactivity was mainly located in the vitreous fluid, retina and aqueous humour at 24 hours post-dose.”

“Data from the 6-week study indicate that administration of patisiran-LNP or AF-011-1955 resulted in transient complement activation after 15 minutes, 6h and 24 h after dosing.”

“Based on male adult rat autoradiography (QWBA) studies with 0.3mg/kg single dose IV patisiran-LNP with radiolabelled 14C-DLin-MC3-DMA, most of the radioactivity (>90%) is rapidly distributed to the liver”

“A low incidence, 3 out of 36 treated monkeys in the 36- week repeat-dose toxicity study (GO1-GLP15-036) were confirmed to have a low titre of anti-lumasiran antibodies.”

“Relatively high tissue concentrations (in descending order) were observed in the liver, kidney cortex, kidney medulla, cecum, salivary gland, bone marrow, thyroid and pancreas.”

“The development of anti-tofersen antibodies was not investigated in the chronic toxicity studies in rat, mice and monkeys.”

“The rapid distribution phase is due to the rapid and broad distribution from the CSF to the CNS tissues with additional clearance due to transfer to the systemic circulation.”

“Fitusiran increased the incidence of hypersensitivity reactions (skin redness/dryness/scab/discharge at the injection site) in rats and monkeys at all doses tested.”

“Fitusiran distributed mainly to liver (the primary target organ of pharmacology), followed by kidney and spleen.”

“No induction of proinflammatory cytokines or inflammation were noted in the completed rat and monkey toxicity studies at doses higher than the plasma concentrations expected at MRHD”

“revealed high liver concentration (>100-fold) compared to other sites and a prolonged liver elimination half-life (~4 to 5 days)”

“No test article-related effect on cytokine activation was evident at any time point evaluated.”

“Nedosiran is distributed primarily to the liver, and to a lesser extent to the kidney.”

“No immunogenicity (e.g., anti-drug antibody) assessment has been conducted.”

“The highest concentration of imetelstat was seen in the liver and kidney, followed by the bone marrow and spleen.”

“In the 14- and 53-week juvenile monkey studies, no drug-related mortality or effects on body weight, ECG, CSF chemistry/cell counts, clinical pathology, or complement activation (as measured by concentrations of Bb split product) were observed”

“Concentrations in systemic tissues like liver and kidney following IT administration were similar to those seen in the spinal cord indicating that a substantial proportion of the administered dose was transferred from CSF to the systemic circulation.”

“In the same study, five other animals across the three lowest dose groups showed perivascular mixed cell infiltration in multiple organs, associated with increases in anti-drug antibody, CRP, IL-6, MIP-1β, TNFα, and serum IgG and IgM”

“High concentrations of inotersen were detected in kidneys, liver, mesenteric lymph nodes, injection site and bone marrow.”

“Dose-dependent increases in complement Bb were seen at all dosages.”

“Distribution to tissues in mouse and monkey was responsible for the initial rapid plasma clearance, with the highest concentrations present in liver and kidney.”

“There were no drug effects on C3 after dosing on Day 0; however, on Day 175, there was an approximate 2-fold elevation in serum C3 24 h after dosing in HDM.”

“With multiple doses (20 mg/kg/week for 8 weeks), highest levels of dose radioactivity were in kidney cortex (819 µg-Eq/g), with concentrations in skeletal muscle of 0.331- 0.479 µg-Eq/g.”

“No drug-related findings were observed in the 12-week study, except for transient (Day 8) increases in complement B6 fragment and C3a at the mid and high doses and a dose-related decrease in FSH (Day 80).”

“The drug was rapidly and extensively distributed to most tissues except CNS (brain and spinal cord). Highest levels of radioactivity were observed in kidney.”

“Thus, these ADAs represent binding antibodies without neutralising capacity.”

“In SD rats administered [3H]ASO-eplontersen, radioactivity levels peaked in plasma at 0.5 h postdose, then distributed into tissues, primarily liver and kidney, with the highest levels observed in the liver at 8 h and kidney at 2 days; radioactivity was undetectable in brain and spinal cord.”

“Complement activation is seen in monkeys, a known effect of antisense oligonucleotides and considered species specific.”

“For all evaluated dose levels, volanesorsen concentrations 48 hours after the last dose (Day 93) were several hundred-to several thousand-fold higher in kidney cortex and liver than in plasma.”

“revealed findings consistent with ASO uptake, accumulation, and a proinflammatory response, including basophilic granules in Kupffer cells, mononuclear cell infiltration in the liver, and vacuolated/granular macrophages in multiple tissues”

“Zilganersen concentrations increased in a dose-dependent manner in maternal and paternal liver, but were very low to undetectable in placenta and fetal liver.”