Pharmacokinetics, pharmacodynamics, and toxicity of a PD-1-targeted IL-15 in cynomolgus monkeys.

PF-07209960 is a novel bispecific fusion protein composed of an anti-PD-1 antibody and engineered IL-15 cytokine mutein with reduced binding affinity to its receptors. The pharmacokinetics (PK), pharmacodynamics (PD), and toxicity of PF-07209960 were evaluated following once every other week subcutaneous (SC) or intravenous (IV) administration to cynomolgus monkeys in a repeat-dose PKPD (0.01-0.3 mg/kg/dose) and GLP toxicity study (0.1-3 mg/kg/dose). PF-07209960 showed dose dependent pharmacokinetics with a terminal T1/2 of 8 and 13 hours following IV administration at 0.03 and 0.1 mg/kg, respectively. The clearance is faster than a typical IgG1 antibody. Slightly faster clearance was also observed following the second dose, likely due to increased target pool and formation of anti-drug antibodies (ADA). Despite a high incidence rate of ADA (92%) observed in GLP toxicity study, PD-1 receptor occupancy, IL-15 signaling (STAT5 phosphorylation) and T cell expansion were comparable following the first and second doses. Activation and proliferation of T cells were observed with largest increase in cell numbers found in gamma delta T cells, followed by CD4+ and CD8+ T cells, and then NK cells. Release of cytokines IL-6, IFNγ, and IL-10 were detected, which peaked at 72 hours postdose. There was PF-07209960-related mortality at ≥1 mg/kg. At scheduled necropsy, microscopic findings were generalized mononuclear infiltration in various tissues. Both the no observed adverse effect level (NOAEL) and the highest non severely toxic dose (HNSTD) were determined to be 0.3 mg/kg/dose, which corresponded to mean Cmax and AUC48 values of 1.15 µg/mL and 37.9 µg*h/mL, respectively.

CD40 agonist-induced IL-12p40 potentiates hepatotoxicity.

BACKGROUND: CD40 is a compelling target for cancer immunotherapy, however, attempts to successfully target this pathway have consistently been hampered by dose-limiting toxicity issues in the clinic that prevents the administration of efficacious doses. METHODS: Here, using cytokine and cytokine receptor depletion strategies in conjunction with a potent CD40 agonist, we investigated mechanisms underlying the two primary sources of CD40 agonist-associated toxicity, hepatotoxicity and cytokine release syndrome (CRS). RESULTS: We demonstrate that CD40 agonist -induced hepatotoxicity and CRS are mechanistically independent. Historical data have supported a role for interleukin-6 (IL-6) in CRS-associated wasting, however, our findings instead show that an inflammatory cytokine network involving TNF, IL-12p40, and IFNγ underlie this process. Deficiency of TNF or IFNγ did not influence CD40-induced hepatitis however loss of IL-12p40 significantly decreased circulating concentrations of liver enzymes and reduced the frequency of activated CD14+MHCII+ myeloid cells in the liver, indicating a role for IL-12p40 in liver pathology. CONCLUSIONS: As clinical research programs aim to circumnavigate toxicity concerns while maintaining antitumor efficacy it will be essential to understand which features of CD40 biology mediate antitumor function to develop both safe and efficacious agonists.

Crizotinib reduces the rate of dark adaptation in the rat retina independent of ALK inhibition.

Crizotinib (Xalkori) is a tyrosine kinase inhibitor of both anaplastic lymphoma kinase (ALK) and mesenchymal-epithelial transition factor (c-Met). Though not predicted from standard nonclinical toxicological evaluation, visual disturbance became a frequently observed adverse event in humans. To understand the possible mechanism of this vision effect, an in vivo electroretinogram (ERG) study was conducted to assess retinal functional changes following oral administration of crizotinib. Immunohistochemical (IHC) staining of ALK and c-Met in the neural retinas of human, non-human primate, dog, rat, and mouse was used to aid in the animal model selection. ALK IHC staining was identified predominantly in the ganglion cell and inner nuclear layers of most species evaluated, in the inner plexiform layer in human and rodent, and in the nerve fiber layer in human and rat only. There was no apparent staining of any layer of the neural retina for c-Met in any of the species evaluated. ERG measurements identified a significant reduction in b-wave amplitude during the initial phase of dark adaptation in the crizotinib-treated rats. ERGs were also taken following oral administration of PF-06463922 (an ALK-selective inhibitor), for an understanding of potential kinase involvement. ERG effects were not observed in PF-06463922-treated animals when comparable exposures in the vitreous humor were achieved. Collectively, our results suggest that the ERG b-wave amplitude decreases during dark adaption following crizotinib administration may be related to signaling changes within the retina in rats, likely independent of ALK inhibition.

PD0325901, a mitogen-activated protein kinase kinase inhibitor, produces ocular toxicity in a rabbit animal model of retinal vein occlusion.

OBJECTIVE: PD0325901, a selective inhibitor of mitogen-activated protein kinase kinase (MEK), was associated with the occurrence of ocular retinal vein occlusion (RVO) during clinical trials in patients with solid tumors. As previous animal safety studies in rats and dogs did not identify the eye as a target organ of toxicity, this work was conducted to develop a rabbit model of ocular toxicity with PD0325901. METHODS: Dutch-Belted rabbits were administered a single intravitreal injection of PD0325901 (0.5 or 1 mg/eye) or saline control, and ophthalmic examinations and retinal angiography were conducted over a 2-week period post-dose. In addition, mechanism of ocular toxicity was further explored in rat with microarray analysis. RESULTS: PD0325901 treatment produced RVO with retinal vasculature leakage and hemorrhage within 48-h postinjection in Dutch-Belted rabbits. Subsequent retinal detachment and degeneration were also detected on day 8 postinjection. To evaluate the potential mechanism(s) of PD0325901-mediated RVO, male Brown Norway rats were orally administered PD0325901 (45 mg/kg/day) up to 5 days and retinal tissue was collected for gene array analysis. Although PD0325901 did not produce clinical evidence of RVO in rats, retinal gene expression suggested an increased oxidative stress and inflammatory response, endothelium and blood-retinal barrier damage, and prothrombotic effects. Moreover, soluble endothelial protein C receptor (sEPCR), a biomarker for RVO, was elevated in human umbilical vascular endothelial cells (HUVECs) cultured with PD0325901. CONCLUSIONS: This work has developed a rabbit model of PD0325901-induced RVO that may be used to characterize the cellular and molecular mechanisms of this effect in humans.