Pharmacokinetic modeling of recombinant interleukin-2 in patients with human immunodeficiency virus infection

Safety, Pharmacokinetics, Pharmacodynamics, and Antitumor Activity from a Phase I Study of Simlukafusp Alfa (FAP-IL2v) in Advanced/Metastatic Solid Tumors

PURPOSE

Simlukafusp alfa [fibroblast activation protein α-targeted IL2 variant (FAP-IL2v)], a tumor-targeted immunocytokine, comprising an IL2 variant moiety with abolished CD25 binding fused to human IgG1, is directed against fibroblast activation protein α. This phase I, open-label, multicenter, dose-escalation, and extension study (NCT02627274) evaluated the safety, pharmacokinetics, pharmacodynamics, and antitumor activity of FAP-IL2v in patients with advanced/metastatic solid tumors.

PATIENTS AND METHODS

Participants received FAP-IL2v intravenously once weekly. Dose escalation started at 5 mg; flat dosing (≤25 mg) and intraparticipant uptitration regimens (15/20, 20/25, 20/20/35, and 20/35/35 mg) were evaluated. Primary objectives were dose-limiting toxicities, maximum tolerated dose, recommended expansion dose, and pharmacokinetics.

RESULTS

Sixty-one participants were enrolled. Dose-limiting toxicities included fatigue (flat dose 20 mg: n = 1), asthenia (25 mg: n = 1), drug-induced liver injury (uptitration regimen 20/25 mg: n = 1), transaminase increase (20/25 mg: n = 1), and pneumonia (20/35/35 mg: n = 1). The uptitration regimen 15/20 mg was determined as the maximum tolerated dose and was selected as the recommended expansion dose. Increases in peripheral blood absolute immune cell counts were seen for all tested doses [NK cells, 13-fold; CD4+ T cells (including regulatory T cells), 2-fold; CD8+ T cells, 3.5-fold] but without any percentage change in regulatory T cells. Clinical activity was observed from 5 mg [objective response rate, 5.1% (n = 3); disease control rate, 27.1% (n = 16)]. Responses were durable [n = 3, 2.8 (censored), 6.3, and 43.4 months].

CONCLUSIONS

FAP-IL2v had a manageable safety profile and showed initial signs of antitumor activity in advanced/metastatic solid tumors.

Sustained in vivo signaling by long-lived IL-2 induces prolonged increases of regulatory T cells

Regulatory T cells (Tregs) expressing FOXP3 are essential for the maintenance of self-tolerance and are deficient in many common autoimmune diseases. Immune tolerance is maintained in part by IL-2 and deficiencies in the IL-2 pathway cause reduced Treg function and an increased risk of autoimmunity. Recent studies expanding Tregs in vivo with low-dose IL-2 achieved major clinical successes highlighting the potential to optimize this pleiotropic cytokine for inflammatory and autoimmune disease indications. Here we compare the clinically approved IL-2 molecule, Proleukin, with two engineered IL-2 molecules with long half-lives owing to their fusion in monovalent and bivalent stoichiometry to a non-FcRγ binding human IgG1. Using nonhuman primates, we demonstrate that single ultra-low doses of IL-2 fusion proteins induce a prolonged state of in vivo activation that increases Tregs for an extended period of time similar to multiple-dose Proleukin. One of the common pleiotropic effects of high dose IL-2 treatment, eosinophilia, is eliminated at doses of the IL-2 fusion proteins that greatly expand Tregs. The long half-lives of the IL-2 fusion proteins facilitated a detailed characterization of an IL-2 dose response driving Treg expansion that correlates with increasingly sustained, suprathreshold pSTAT5a induction and subsequent sustained increases in the expression of CD25, FOXP3 and Ki-67 with retention of Treg-specific epigenetic signatures at FOXP3 and CTLA4.

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Fusion of IL-2 to human IgG1 extends IL-2 half-life and efficiency of Treg induction.

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Long-lived IL-2 efficacy allows for lower doses thereby increasing Treg specificity.

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Sustained pSTAT5a induction in Tregs by long-lived IL-2 correlates with Treg expansion.

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Increased stoichiometry, IgG-(IL-2)₂, increases affinity and in vivo effects on Tregs

Interleukin 15 provides relief to CTLs from regulatory T cell-mediated inhibition: implications for adoptive T cell-based therapies for lymphoma

PURPOSE

Systemic administration of recombinant interleukin (IL)-2 is used to support the expansion and persistence of adoptively transferred antigen-specific CTLs in patients with cancer. However, IL-2 also expands regulatory T cells (Treg) that in turn impair the antitumor activity of CTLs. As recombinant IL-15 is approaching clinical applications, we assessed the effects of this cytokine on the proliferation and antitumor activity of CTLs in the presence of Tregs. We used the model of adoptive transfer of Epstein-Barr virus (EBV)-CTLs, as these cells induce responses in patients with EBV-associated Hodgkin lymphoma, and Tregs are frequently abundant in these patients.

EXPERIMENTAL DESIGN

Tregs were isolated from the peripheral blood of healthy donors and patients with Hodgkin lymphoma or from Hodgkin lymphoma tumors and assessed for their ability to inhibit the proliferation and antitumor activity of EBV-CTLs in the presence of IL-15 or IL-2. Specific molecular pathways activated by IL-15 were also explored.

RESULTS

We found that in the presence of Tregs, IL-15, but not IL-2, promoted the proliferation, effector function, and resistance to apoptosis of effectors T cells and EBV-CTLs. IL-15 did not reverse or block Tregs but instead preferentially supported the proliferation of CTLs and effector T cells as compared with Tregs.

CONCLUSIONS

IL-15 selectively favors the survival, proliferation, and effector function of antigen-specific CTLs in the presence of Tregs, and thus IL-15, unlike IL-2, would have a significant impact in sustaining expansion and persistence of adoptively transferred CTLs in patients with cancer, including those infused with EBV-CTLs for treatment of EBV-associated malignancies.

A validated assay to measure soluble IL-7 receptor shows minimal impact of IL-7 treatment

IL-7 is a crucial cytokine for T cell hematopoiesis and peripheral homeostasis which by signaling through its receptor alpha chain (CD127) is essential for inducing T cell proliferation and survival. Since the specific CD127 alpha chain is found in a soluble state (sCD127) and at a high level in plasma (ng/mL), it is important to develop a sensitive and reliable assay in order to investigate the potential role of this receptor in the regulation of IL-7 physiologic, physipathologic and therapeutic effects. We here report a fully validated method to measure sCD127 in human and simian plasma using a method based on ELISA MSD technology. We demonstrate that sCD127 is detectable at various levels in the plasma of healthy humans as well as in that of healthy Rhesus and Cynomolgus macaques (106.72, 205.26 and 366.95 ng/mL respectively). Moreover, as opposed to the sCD25/IL-2 tandem, we demonstrate that IL-7 treatment has no impact on sCD127 plasma concentration in patients infected by HIV.

Safety, tolerability, pharmacokinetics, and efficacy of an interleukin-2 agonist among HIV-infected patients receiving highly active antiretroviral therapy

We sought to determine the safety, maximum tolerated dose, optimal dose, and preliminary dose efficacy of intermittent subcutaneously (s.c.) administered BAY 50-4798 among patients with HIV infection receiving highly active antiretroviral therapy (HAART) compared with patients receiving HAART alone. A phase I/II randomized, double-blind, dose-escalation study was conducted of the safety, tolerability, pharmacokinetics, and efficacy of s.c. BAY 50-4798 administered to HIV-infected patients already receiving stable HAART. There were no unexpected safety findings in a population of HIV-infected patients receiving HAART plus SC BAY 50-4798 as adjunctive therapy. BAY 50-4798 exhibited nearly dose-proportional pharmacokinetics, and accumulation was minimal during multiple-dose treatment. Limited efficacy data indicated that treatment with BAY 50-4798 caused at least a transient increase in CD4(+) T cell counts in some recipients, particularly at the early time points. In general, this effect appeared to increase with increasing dose. Bay 50-4798 was generally well tolerated across the dose range tested, but a lack of potent, sustained immunologic activity suggests that further optimization of dose and schedule will be necessary.

Kupffer cell-mediated IL-2 suppression of CYP3A activity in human hepatocytes

Interleukin (IL)-2 administration has been shown to decrease CYP3A enzyme activity in vivo. To determine whether IL-2 suppression of human hepatocyte CYP3A activity is direct or whether it is facilitated by the presence of Kupffer cells, primary human hepatocytes were cultured alone or cocultured with primary human Kupffer cells at physiologic hepatocyte/Kupffer cell ratios of 10:1 or 10:4. Using proinflammatory cytokines as positive controls, IL-1 (0.2-20 ng/ml) and IL-6 (2-200 ng/ml) exposure resulted in a 70 to 90% decrease in CYP3A activity after 72 h in hepatocyte cultures. In the hepatocyte/Kupffer cell cocultures, an 80% decrease in CYP3A activity was observed with IL-1 (2 ng/ml) or IL-6 (20 ng/ml), suggesting that direct suppressive effects of proinflammatory cytokines on hepatocyte CYP3A activity are not substantially altered by Kupffer cells. In contrast to the effects of these proinflammatory cytokines, no sustained suppression of CYP3A activity was observed with IL-2 (2-200 ng/ml) in hepatocyte cultures. However, in hepatocyte/Kupffer cell cocultures, a concentration-dependent 50 to 70% suppression of CYP3A activity was observed with IL-2 at 72 h. In summary, these data suggest that Kupffer cells are required to reconstitute the suppressive effects of IL-2 on CYP3A activity that are observed in vivo and that hepatocyte/Kupffer cell cocultures may provide a useful model for investigating mechanisms of CYP3A4 regulation by cytokines. Of particular relevance to certain hepatic diseases, these findings suggest potential mechanisms whereby cytokines released from infiltrating blood mononuclear cells might modulate intercellular signaling and controls on hepatocyte function by various cell types that reside in liver.

A randomized controlled trial evaluating the efficacy and safety of intermittent 3-, 4-, and 5-day cycles of intravenous recombinant human interleukin-2 combined with antiretroviral therapy (ART) versus ART alone in HIV-seropositive patients with 100-300 CD4+ T cells

The effect of length of therapy on the safety and efficacy profile of continuous intravenous (CIV) interleukin-2 (IL-2) in combination with antiretroviral therapy (ART) was evaluated in 81 HIV-seropositive patients with CD4(+) T-cell counts of 100-300/mm(3). Patients were randomized to CIV IL-2 (12 mIU/day) for 3, 4, or 5 days plus ART every 8 weeks for six cycles, or to ART alone. The mean percent increase in CD4(+) T-cell counts was 24.5% for IL-2 recipients compared with a mean percent decrease of 30.5% for control patients (P = 0.005). Increasing duration of CIV IL-2 therapy resulted in improved CD4(+) T-cell response. The most frequent clinical adverse events and laboratory abnormalities were predominantly of grade 1 or 2 severity. However, grade 3 or 4 events were reported in 57%, 60%, and 84% of the 3-, 4-, and 5-day CIV IL-2 patients, respectively. Serious adverse events, mainly due to the requirement of hospitalization, occurred in 20% of IL-2 recipients, compared with 10% of control patients. Viral load during the course of the study was not different among the treatment groups. IL-2 therapy in cycles of 5 days resulted in an optimal increase in CD4(+) T-cell counts and is the preferred cycle length for IL-2 therapy geared toward increasing CD4(+) T-cell numbers.

Pharmacokinetics of histamine dihydrochloride in healthy volunteers and cancer patients: implications for combined immunotherapy with interleukin-2

Recent clinical trials in melanoma and leukemia have demonstrated potential for increased survival time and improved remission when histamine dihydrochloride is added to cytokine monotherapy. In the present study, the pharmacokinetics of subcutaneous histamine (1 mg) in 21 healthy subjects and 12 melanoma patients was determined via model-dependent methods. Drug-drug interactions with subcutaneous interleukin-2 (1.1 mg) were evaluated in a combined cohort of patients with melanoma (n = 8) or renal cell carcinoma (n = 4). Histamine dihydrochloride administered over 10 minutes in healthy subjects peaked at 18 minutes (Cmax 38 nmol/L), attained a distribution volume of 59 L, and was eliminated at 6%/min. The results were similar in a 20-minute infusion in melanoma patients. No gender effects were observed (p > 0.05). Interleukin-2 injected either 10 minutes prior to or 10 minutes following histamine dihydrochloride had no effect on histamine kinetics. Histamine dihydrochloride administered 10 minutes prior to injection of interleukin-2 also had no effect on interleukin-2 kinetics. Maximal concentration of interleukin-2 (2,442 pg/ml) occurred at 2.5 hours with an elimination half-life of 1.7 hours, area under the curve (AUC) of 15,746 pg x h/ml, and volume of distribution and plasma clearance of 194 L and 74 L/h, respectively. However, interleukin-2 Cmax (1,758 pg/ml) and AUC (12,448 pg x h/ml) were reduced when histamine dihydrochloride was infused 10 minutes following interleukin-2, likely due to the pharmacodynamic effects of histamine, including increased heart rate and reduced blood pressure. It is concluded that histamine dihydrochloride and interleukin-2 can be safely coadministered with minimal interaction.

Tumor necrosis factor alpha, interleukin 2, and soluble interleukin 2 receptor levels in human immunodeficiency virus type 1-infected individuals receiving intermittent cycles of interleukin 2

HIV-infected individuals with 200-500 CD4(+) T cell/microl were enrolled in a controlled study of three interleukin 2 (IL-2) plus antiretroviral therapy (ART) regimens: (1) continuous intravenous administration of 12 million international units (MIU) of IL-2 followed by subcutaneous high-dose IL-2 (7.5 MIU, twice daily) for 5 days every 8 weeks; (2) high-dose subcutaneous IL-2 for 5 days every 8 weeks; (3) low-dose (3 MIU, twice daily) subcutaneous IL-2 for 5 days every 4 weeks; and (4) ART alone. Serum concentrations of IL-2, soluble IL-2 receptor (sIL-2R), tumor necrosis factor alpha (TNF-alpha), and IL-6 were determined. A progressive decrease over time of the circulating levels of IL-2 was observed in individuals receiving the highest doses of IL-2, but not in those belonging to the low-dose arm. Conversely, increased levels of sIL-2R were observed in all cytokine-treated individuals. The levels of TNF-alpha increased in the high-dose IL-2 regimens, but decreased in individuals receiving low-dose IL-2. IL-2-related toxicity was significantly correlated to the peak IL-2 serum levels, and was substantially lower in those individuals receiving low-dose IL-2. In conclusion, intermittent IL-2 administration causes the elevation of peripheral CD4(+) T cells, but also a profound cytokine response and systemic toxicity. The latter was correlated to the peak serum level of IL-2, but not to those of TNF-alpha and IL-6.