ALBERT

Description: Background: IL-15-mediated responses have been shown to have a crucial role in the development, function, and survival of CD8+ T cells, natural killer (NK) cells, and NK T cells. However, exploiting native IL-15 is challenging due to its unfavorable pharmacokinetics and tolerability. NKTR-255 is a polymer-conjugated IL-15 that retains binding affinity to IL-15Ra, maintaining full spectrum of IL-15 biology. NKTR-255 also exhibits improved pharmacokinetics, thereby providing sustained pharmacodynamic responses without the need for daily dosing. Studies have indicated that NK cells from patients with multiple myeloma (MM) appear to be dysfunctional, and successful activity against MM cells requires highly active NK cells ideally activated from immunomodulatory agents or cytokine support. In recent years, several new agents have been introduced in the MM landscape to engage NK-mediated myeloma cell elimination, including the CD38-targeting monoclonal antibody daratumumab, and elotuzumab, further supporting the anti‐MM effect of NK cells in the post-autologous transplant setting. In non-Hodgkin lymphoma (NHL), studies have shown low peripheral blood NK cell counts are associated with poor clinical outcomes in diffuse large B-cell lymphoma patients receiving R-CHOP chemotherapy regimens. Recently published data indicate that NKTR-255 in combination with CAR T cells decreases tumor burden and increases survival compared to CAR T cells alone. NKTR-255 may address the need to boost NK cell quality and numbers in these patients with the purpose of aiding current approved therapies. Methods: In this phase 1, open-label, multi-center, dose escalation and dose expansion study of NKTR-255, patients with relapsed or refractory (r/r) MM or NHL with no available therapies will be eligible. In the dose escalation portion, approximately 46 patients will be enrolled. Successive cohorts of 3 patients each will receive single increasing doses of NKTR-255 until the maximum tolerated dose (MTD) is determined. All patients will receive NKTR-255 once every three weeks. Patients will be observed for a dose-limiting toxicity (DLT) window of three weeks following the first NKTR-255 dose. A two-parameter Bayesian logistic regression model (BLRM) will be used during the escalation part of the study for dose level selection and for determination of MTDs. The selected recommended phase 2 dose (RP2D) of NKTR-255 will be evaluated in two dose expansion cohorts. Cohort A will expand NKTR-255 in patients with r/r MM or NHL as a salvage regimen to further characterize safety and tolerability. Cohort B will combine NKTR-255 with daratumumab in patients with MM with progressive disease who have had at least 3 prior lines of therapy with no other regimens that would confer clinical benefit. Daratumumab will be administered IV at the standard approved regimen. The primary objectives of the study are to evaluate: safety, tolerability, MTD, and RP2D of NKTR-255 as a single agent, as well as safety and tolerability of NKTR-255 in combination with daratumumab in patients with r/r MM. Secondary objectives include measures biomarker and pharmacokinetic analyses. Figure Disclosures Shah: University of California, San Francisco: Employment; Nkarta: Consultancy, Membership on an entity's Board of Directors or advisory committees; Kite: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celgene, Janssen, Bluebird Bio, Sutro Biopharma: Research Funding; Poseida: Research Funding; Bristol-Myers Squibb: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Teneobio: Consultancy, Membership on an entity's Board of Directors or advisory committees; Genentech, Seattle Genetics, Oncopeptides, Karoypharm, Surface Oncology, Precision biosciences GSK, Nektar, Amgen, Indapta Therapeutics, Sanofi: Membership on an entity's Board of Directors or advisory committees; Indapta Therapeutics: Equity Ownership. Turtle:Nektar Therapeutics: Other: Ad hoc advisory board member, Research Funding; T-CURX: Membership on an entity's Board of Directors or advisory committees; Allogene: Other: Ad hoc advisory board member; Humanigen: Other: Ad hoc advisory board member; Eureka Therapeutics: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Juno Therapeutics: Patents & Royalties: Co-inventor with staff from Juno Therapeutics; pending, Research Funding; Precision Biosciences: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Caribou Biosciences: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Kite/Gilead: Other: Ad hoc advisory board member; Novartis: Other: Ad hoc advisory board member. Cowan:Cellectar: Consultancy; Juno: Research Funding; Sanofi: Consultancy; Janssen: Consultancy, Research Funding; Celgene: Consultancy, Research Funding; Abbvie: Research Funding. Chavez:Kite: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novartis: Membership on an entity's Board of Directors or advisory committees; Genentech: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Bayer: Membership on an entity's Board of Directors or advisory committees; Karyopharm: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees. Budde:F. Hoffmann-La Roche Ltd: Consultancy. Marcondes:Nektar Therapeutics: Employment, Equity Ownership. Lee:Nektar Therapeutics: Employment. Lin:Nektar Therapeutics: Employment, Equity Ownership. Zalevsky:Nektar Therapeutics: Employment, Equity Ownership. Tagliaferri:Nektar Therapeutics: Employment, Equity Ownership. Patel:Poseida Therapeutics, Cellectis, Abbvie: Research Funding; Oncopeptides, Nektar, Precision Biosciences, BMS: Consultancy; Takeda, Celgene, Janssen: Consultancy, Research Funding.

Description: XmAb2513 is a novel humanized monoclonal antibody (mAb) that binds to the human cell surface antigen CD30 and demonstrates anti-proliferative activity against CD30-positive (CD30+) cell lines. XmAb2513 also has an engineered Fc region to enhance cell killing activity via recruitment of effector cells through increased binding affinity to Fcγ receptors (FcγRs). Consequently, XmAb2513 exhibits superior antibody-dependent cell-mediated cytotoxicity (ADCC) and antibody-dependent cell-mediated phagocytosis (ADCP), when compared to a native IgG1 (unengineered) version of the antibody. To evaluate the potential clinical activity of XmAb2513 in CD30+ diseases such as Hodgkin Lymphoma (HL) and Anaplastic Large Cell Lymphoma (ALCL), XmAb2513 was tested in murine subcutaneous xenograft models of HL using the CD30+ L540 cell line. In the ICR-SCID mouse strain, intraperitoneal (ip) administration of XmAb2513 at 3 mg/kg every 4 days for 10 doses (q4d ×10), gave a statistically significant reduction in tumor growth and enhanced survival relative to the control. At doses of 10 and 30 mg/kg XmAb2513 (ip, q4d ×10) tumor growth was not only slowed, but elimination of established tumors was observed in 3/9 and 5/9 animals respectively. The treatment was well-tolerated. Preclinical studies were conducted to evaluate the safety and pharmacokinetics of XmAb2513 in large animals. In vitro studies demonstrated that the cynomolgus monkey was the appropriate species for study. Binding affinities of XmAb2513 to both human and cynomolgus monkey CD30 and FcγRs were evaluated by Biacore methods and were found to be similar. Additionally, fluorescein-XmAb2513 gave similar staining patterns in immunohistochemistry cross-reactivity studies with normal human and cynomolgus monkey tissue panels. As evidenced by in-life observations single (0, 1 and 100 mg/kg XmAb2513, intravenous [iv] infusion) and repeat dose (0, 10, 30 and 100 mg/kg XmAb2513, q5d ×6, iv infusion) treatment with XmAb2513 was well-tolerated. Serum cytokines showed no trend that was indicative of an XmAb2513-related effect following single dose administration. The pharmacokinetics of XmAb2513 was also determined after either single or repeat dose administration. In the repeat dose study (0, 3, 10 and 30 mg/kg XmAb2513, q5d ×6, iv infusion) exposure increased in a dose proportional manner, and terminal half-life (t1/2) ranged from 12–17 days. In the single dose study (0, 1 and 100 mg/kg XmAb2513, iv infusion) exposure was also proportional to dose. The exposure and t1/2 data support an every other week dosing interval in the clinic. These preclinical data provide a rationale for the clinical testing of XmAb2513 in patients with hematologic malignancies that express CD30, specifically HL and ALCL, and support the safety of repeat administration of XmAb2513 in humans.

Description: CD19, a B cell–restricted receptor critical for B-cell development, is expressed in most B-cell malignancies. The Fc-engineered anti-CD19 antibody, XmAb5574, has enhanced Fcγ receptor (FcγR) binding affinity, leading to improved FcγR-dependent effector cell functions and antitumor activity in murine xenografts compared with the non–Fc-engineered anti-CD19 IgG1 analog. Here, we use XmAb5574 and anti-CD19 IgG1 to further dissect effector cell functions in an immune system closely homologous to that of humans, the cynomolgus monkey. XmAb5574 infusion caused an immediate and dose-related B-cell depletion in the blood (to

Description: XmAb2513 is a novel second-generation humanized monoclonal antibody (mAb) directed against the human cell surface antigen CD30, with an Fc region engineered to enhance cell killing activity via recruitment of effector cells through increased binding affinity to Fcγ receptors (FcγRs). The CD30 antigen (Ki-1) is a member of the tumor necrosis factor superfamily and was originally identified as a cell surface antigen on primary and cultured Reed-Sternberg cells of Hodgkin Lymphoma (HL). Expression of CD30 is a hallmark for the identification of HL and a subset of T-cell lymphomas, including Anaplastic Large Cell Lymphoma (ALCL). Preclinical in vitro data demonstrated XmAb2513 to be more potent with regards to antibody-dependent cell-mediated cytotoxicity (ADCC) and antibody-dependent cell-mediated phagocytosis (ADCP) than the first generation anti- CD30 antibodies MDX-060 and SGN-30. Studies in cynomolgus monkeys demonstrated that XmAb2513 exposure was proportional to dose with half-lives (t½) ranging from 5 to 9 days in single dose studies and 12 to 17 days in repeat dose studies. The exposure and t½ data from these cynomolgus monkey studies supported an every other week dosing interval in clinical trials. Based on these favorable features, a Phase 1 study has been initiated to examine the safety and efficacy of XmAb2513 in patients with relapsed and refractory classical HL and ALCL. This ongoing Phase 1 Study is currently evaluating every other week dosing of XmAb2513 using a dose-escalation study design to establish the maximum tolerated dose (MTD). The dose levels under evaluation are 0.3, 1.0, 3.0, 6.0, 9.0, and 12.0 mg/kg, given intravenously over two hours. To date, seven patients are enrolled on the study in the first three dose levels. Pre-study simulation of human exposure based on the pharmacokinetic (PK) parameters obtained from cynomolgus monkeys predicted that 0.3 mg/kg XmAb2513 in humans would result in serum trough levels of 1–1.5 μg/mL after four infusions given every other week. Interim PK and immunogenicity results from the treated patients have been analysed and the results observed thus far are on track with these simulations. Additionally, immunogenicity assessment for human anti-XmAb2513 (HAHA) showed that the treated patients are so far negative for HAHA. Importantly XmAb2513 was well tolerated. As dose escalation continues, results for human PK, immunogenicity, and safety for additional dose cohorts of HL patients, and preliminary safety and response assessment data will be presented.

Description: XmAb®5574 is an Fc engineered humanized monoclonal antibody (mAb) that binds to the human cell surface antigen CD19 and demonstrates anti-proliferative activity against CD19-positive (CD19+) cell lines. XmAb5574 also has an engineered Fc region to enhance cell killing activity via recruitment of effector cells through increased binding affinity to Fcγ receptors (FcγRs). Consequently, XmAb5574 exhibits superior antibody-dependent cell-mediated cytotoxicity (ADCC) and antibody-dependent cell-mediated phagocytosis (ADCP), when compared to a native IgG1 (non Fc-engineered) or an Fc knock out (Fc KO; engineered to ablate FcγR interaction) version of the anti-CD19 antibody. To evaluate the potential clinical activity of XmAb5574 in CD19+ B cell malignancies such as non-Hodgkin’s lymphoma (NHL), XmAb5574 was tested in murine subcutaneous (sc) xenograft models using the CD19+ Ramos and Raji human lymphoma cell lines. XmAb5574, administered by intraperitoneal injection (ip, 2qw ×2), gave dose-related inhibition of tumor growth with these models. The efficacy against established sc Ramos tumors was shown to be FcγR-dependent and enhanced by Fc engineering. Fc KO antibodies had no effect at the doses used. Preclinical studies were conducted to evaluate the safety and pharmacokinetics of XmAb5574 in non-human primates. In vitro studies demonstrated that the cynomolgus monkey was an appropriate species for study. XmAb5574 bound to a CD19-expressing cynomolgus monkey cell line and CD20+ peripheral lymphocytes from either cynomolgus monkey or human whole blood samples. Binding affinities of XmAb5574 to both human and cynomolgus monkey FcγRs were evaluated by Biacore methods and were found to be similar. Additionally, XmAb5574 gave similar staining patterns in immunohistochemistry cross-reactivity studies with normal human and cynomolgus monkey tissue panels. Single dose administration of XmAb5574 (0, 0.3, 1.0, 3.0, and 10.0 mg/kg, intravenous [iv] infusion) to cynomolgus monkeys gave an immediate and sustained depletion of peripheral B cells in a dose-dependent manner. B cells were reduced in the bone marrow and lymph node with the spleen showing involuted germinal centers and decreased CD20 immunostaining. B cell recovery, peripherally evident after 57 days, was observed in lymphoid tissues after 85 days. The native anti-CD19 IgG1 (non Fc-engineered) did not induce B cell depletion at 3 mg/kg, in contrast to almost complete B cell depletion by XmAb5574 at the same dose. The pharmacokinetics of XmAb5574 were determined in cynomolgus monkeys after a single iv infusion at 0.3, 1, 3, or 10 mg/kg. Blood samples were collected throughout the study, processed to serum, and XmAb5574 concentration determined using an ELISA method. Exposure was approximately dose proportional for the 1–10 mg/kg dose levels but decreased at the 0.3 mg/kg level indicating dose-dependent clearance for XmAb5574 in this species. Among the 1–10 mg/kg dose levels, the clearance and half-life ranged from 4.3–5.8 mL/day and 7.7–10.7 days, respectively. Single iv infusions of XmAb5574 (0.3–10 mg/kg) were well tolerated in cynomolgus monkeys. These preclinical data provide a rationale for the clinical testing of XmAb5574 in patients with B cell malignancies.

Description: Introduction IL-15 is a common gamma chain cytokine that activates and provides a survival benefit to T-cells and NK cells and has long been recognized as having potential as an immunotherapeutic agent for the treatment of cancer. Therapeutic use of native IL-15 has been challenging due to, for example, its unfavorable pharmacokinetic and safety properties. NKTR-255 is a polymer-conjugated human IL-15 that retains binding affinity to the alpha subunit of IL-15 receptor and exhibits reduced clearance to thereby provide a sustained pharmacodynamics response. Here we investigate the biological effects of NKTR-255 in naïve cynomolgus monkey. Methods In vitro monkey whole blood was treated with NKTR255 and the percentage of pSTAT5 positive populations in each NK, CD4 T and CD8 T cells was determined by flow cytometry. In an PK/PD study, monkeys received single IV doses of 0.001, 0.003, 0.01, 0.03, or 0.1 mg/kg NKTR-255. Blood samples were collected to determine the plasma concentrations of NKTR-255 and to assess the effects of NKTR-255 on NK and CD8 T cells at multiple time points; flow cytometry was used to measure STAT5 phosphorylation, Ki-67 expression and frequency of cell populations. Granzyme B expression was assessed in NK and CD8 T cells by flow cytometry. Results NKTR-255 induced dose-dependent phosphorylation of STAT5 in monkey whole blood (EC50 values NK cells: 6.9 ng/ml, CD8 T cells: 39 ng/ml, CD4 T cells: 53 ng/ml). The half-life and clearance of NKTR-255 were 26x longer and 38x lower, respectively, than IL-15. NKTR-255 engaged the IL-15 signaling pathway, in vivo, demonstrating both robust and sustained STAT5 phosphorylation in lymphocytes. NKTR-255 drove the proliferation of total CD8 T cells and NK cells in a dose-dependent manner, with dramatic and durable increases observed in Ki67 positive population and absolute cell numbers (NK cells: 6.1 fold; CD8 T cells: 7.8 fold from baseline on day 5 at 0.1 mg/kg). These effects were strongly biased towards CD8 T cells and NK cells, with substantially less induction of CD4 T cells. The Ki67 response analyses of the T cell subpopulation revealed a higher response of memory populations than for naive T cells. Among memory T cells, effector memory T cells showed the highest response over stem cell memory T cells and central memory T cells. Finally, NKTR-255 also increased the expression of Granzyme B in both NK and CD8 T cells, concomitant with an enhancement in target cell lysis. Conclusions Nektar has generated a novel and potent molecule in NKTR-255 that not only preserves the relevant biology of IL-15, but additionally provides enhanced PK and PD properties relative to the native IL-15 cytokine. NKTR-255 is being developed as an immune-stimulatory agent to target NK and CD8 T cell biology for the treatment of cancer. Disclosures Miyazaki: Nektar Therapeutics: Employment, Equity Ownership. Kuo:Nektar Therapeutics: Employment, Equity Ownership. Maiti:Nektar Therapeutics: Employment, Equity Ownership. Obalapur:Nektar Therapeutics: Employment, Equity Ownership. Addepalli:Nektar Therapeutics: Employment, Equity Ownership. Rubas:Nektar Therapeutics: Employment, Equity Ownership. Sims:Nektar Therapeutics: Employment, Equity Ownership. Zhang:Nektar Therapeutics: Employment, Equity Ownership. Madakamutil:Nektar Therapeutics: Employment, Equity Ownership. Zalevsky:Nektar Therapeutics: Employment, Equity Ownership.

Description: Background IL-15 is a cytokine that activates and provides survival benefit to T and NK cells and has great potential as an immunotherapeutic agent for the treatment of cancer. Exploiting the therapeutic value of native IL-15 has been challenging due to its unfavorable pharmacokinetic properties and poor tolerability. NKTR-255 is a polymer-conjugated IL-15 designed to retain binding affinity to the IL-15 receptor alpha chain and have decreased clearance to provide a sustained pharmacodynamics response. NKTR-255 has an enhanced immunotherapeutic effect when combined with certain targeted monoclonal antibodies that mediate tumor killing by antibody dependent cellular cytotoxicity (ADCC). Here we further characterized the effect of NKTR-255 on NK cell-mediated ADCC in a B cell lymphoma model. Methods For in vitro ADCC, NKTR-255 pre-treated human NK cells (effector cells) were co-cultured with RPMI-8226 (target cells) and with daratumumab for 3 hours. The ability of NK cells to lyse target cells was evaluated by detecting 7-AAD stained RPMI-8226. In the Daudi lymphoma model, SCID or SCID beige mice were inoculated IV with 1x107 Daudi cells on Day 0. NKTR-255 (0.3 mg/kg IV) was administered on Days 14, 21 and 28 and a single dose of antibody treatment was given on Day 14 (daratumumab 0.5 mg/kg IP). Survival rate was determined by onset of hind limb paralysis or moribundity as surrogate parameters. Concurrent vs staggered regimen assessment was conducted with NKTR-255 dosed on day 14 and daratumumab on Day 14, 17, or 21. For dose examination, high (0.5 mg/kg) and low (0.05 mg/kg) doses of daratumumab were combined with low (0.03 mg/kg) and high (0.3 mg/kg) doses of NKTR-255 in a concurrent manner. Daudi cells in the bone marrow were assessed 10 days after the NKTR-255 dose by flow cytometry. Results In vitro, NKTR-255 pre-treatment of human purified NK cells enhanced daratumumab-mediated ADCC against RPMI-8226. The ability of NKTR-255 to enhance in vitro ADCC was translated into an enhanced therapeutic efficacy of daratumumab in the Daudi lymphoma model with SCID mice. NKTR-255 combined with daratumumab synergistically provided long-term survival benefit in a NKTR-255 dose-dependent manner. To confirm the contribution of NK cells as effector cells for ADCC in vivo, the therapeutic effect of the combination treatment was assessed in the tumor model in SCID beige mice, which have a selective impairment of NK cell cytotoxic function. The long-term survival benefit by the combination treatment, which was observed in SCID mice (median survival of 27 days in control and 59.5 days in treatment), was attenuated in SCID beige mice (median survival of 23 days in control and 30 days in treatment). Concurrent vs staggered dose regimens and dose ranging for NKTR-255 and daratumumab were evaluated in the Daudi model with SCID mice to understand optimal therapeutic use of NKTR-255 in future clinical studies. Tumor depletion in bone marrow was most effective in concurrent treatment of NKTR-255 and daratumumab and three days-staggered treatment (NKTR-255 first and the antibody 3 days later). In contrast, a 7-day stagger showed no benefit of the combination in tumor depletion. Combination of low dose daratumumab and high dose NKTR-255 was equally effective in tumor depletion as a combination of high dose daratumumab and low dose NKTR-255. Conclusions NKTR-255 was shown to enhance in vivo therapeutic efficacy of daratumumab, a monoclonal antibody that mediates tumor killing by ADCC. The effect was mainly mediated by NK cells. The treatment scheduling experiments demonstrated that antibody should be present during NKTR-255-driven NK cell activation/expansion phase to efficiently deplete Daudi tumor cells in bone marrow. In addition, even low dose of daratumumab treatment showed effective tumor depletion when combined with high dose of NKTR-255. This suggests that NKTR-255 has a potential to expand the therapeutic window of existing tumor-targeted antibodies to patients with, for example, low antibody concentration in target tumor site or low expression of tumor antigen. Disclosures Miyazaki: Nektar Therapeutics: Employment, Equity Ownership. Kivimäe:Nektar Therapeutics: Employment, Equity Ownership. Hennessy:Nektar Therapeutics: Employment, Equity Ownership. Pena:Nektar Therapeutics: Employment, Equity Ownership. Quach:Nektar Therapeutics: Employment, Equity Ownership. Moffet:Nektar Therapeutics: Employment, Equity Ownership. Nieves:Nektar Therapeutics: Employment, Equity Ownership. Zhang:Nektar Therapeutics: Employment, Equity Ownership. Marcondes:Nektar Therapeutics: Employment, Equity Ownership. Madakamutil:Nektar Therapeutics: Employment, Equity Ownership. Zalevsky:Nektar Therapeutics: Employment, Equity Ownership.