Optimizing Early Clinical Investigations in Cancer Immunotherapy: The Translational Journey of RG6292, a Novel, Selective Treg-Depleting Antibody

The multifaceted IL-2/IL-2R biology and its modulation by promising therapeutic agents are highly relevant topics in the cancer immunotherapy field. A novel CD25-Treg-depleting antibody (Vopikitug, RG6292) has been engineered to preserve IL-2 signaling on effector T cells to enhance effector activation and antitumor immunity, and is currently being evaluated in the clinic. The Entry into Human-enabling framework described here investigated the characteristics of RG6292, from in vitro quantification of CD25 and RG6292 pharmacology using human tissues to in vivo assessment of PK/PD/safety relationships in cynomolgus monkeys as non-human primate species (NHP). Fundamental knowledge on CD25 and Treg biology in healthy and diseased tissues across NHP and human highlighted the commonalities between these species in regard to the target biology and demonstrated the conservation of RG6292 properties between NHP and human. The integration of in vitro and in vivo PK/PD/safety data from these species enabled the identification of human relevant safety risks, the selection of the most appropriate safe starting dose and the projection of the pharmacologically-relevant dose range. The first clinical data obtained for RG6292 in patients verified the appropriateness of the described approaches as well as validated the full clinical relevance of the projected safety, PK, and PD profiles from animal to man. This work shows how the integration of mechanistic non-clinical data increases the predictive value for human, allowing efficient transition of drug candidates and optimizations of early clinical investigations.

Phase II study to determine the anti-tumor activity and safety of simlukafusp alfa (FAP-IL2v) combined with atezolizumab in esophageal cancer

PURPOSE

Reported here are results from the esophageal squamous cell carcinoma (SCC) cohort of a Phase II, non-comparative, basket study, evaluating the anti-tumor activity and safety of FAP-IL2v plus atezolizumab in patients with advanced/metastatic solid tumors (NCT03386721).

EXPERIMENTAL DESIGN

Eligible patients had an Eastern Cooperative Oncology Group performance status of 0-1; measurable metastatic, persistent, or recurrent esophageal SCC; progression on ≥1 prior therapy; and were checkpoint inhibitor naive. Patients received FAP-IL2v 10 mg plus atezolizumab 1200 mg intravenously every 3 weeks, or FAP-IL2v weekly for 4 weeks, then every 2 weeks, plus atezolizumab 840 mg intravenously every 2 weeks. Primary endpoint was investigator-assessed objective response rate (ORR).

RESULTS

In the response-evaluable population (N=34), best confirmed ORR was 20.6% (95% confidence interval [CI]: 10.4-36.8) with a complete response (CR) seen in one patient and partial responses (PR) in six patients. Disease control rate was 44.1% (CR=2.9%; PR=17.6%; stable disease [SD]=23.5%) and median duration of response was 10.1 months (95% CI: 5.6-26.7). Median progression-free survival was 1.9 months (95% CI: 1.8-3.7). Analysis of response by PD-L1 expression (Ventana SP263) resulted in an ORR of 26.7 % for patients with PD-L1-positive tumors (tumor area positivity [TAP] cut-off ≥1%; n=15) and 7.1% for patients with PD-L1-negative tumors (TAP cut-off <1%; n=14). Overall, the treatment combination was tolerable and adverse events were consistent with the known safety profiles of each drug.

CONCLUSIONS

FAP-IL2v plus atezolizumab demonstrated clinical activity and was tolerable in patients with previously treated esophageal SCC.

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

PURPOSE

Simlukafusp alfa (FAP-IL2v), a tumor-targeted immunocytokine, comprising an interleukin-2 variant moiety with abolished CD25 binding fused to human immunoglobulin G1, 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.

METHODS

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

RESULTS

Sixty-one participants were enrolled. DLTs included fatigue (flat dose 20 mg: n = 1), asthenia (25 mg: n = 1), drug-induced liver injury (up-titration regimen 20/25 mg: n = 1), transaminase increase (20/25 mg: n = 1), and pneumonia (20/35/35 mg: n = 1). Up-titration regimen 15/20 mg was the MTD and was selected as the recommended expansion dose. Increases in peripheral blood absolute immune cell counts were seen for all tested doses (natural killer cells, 13-fold; CD4+ T cells [including Tregs], 2-fold; CD8+ T cells, 3.5-fold), but without any percentage change in Tregs. 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.

Obinutuzumab Pretreatment as a Novel Approach to Mitigate Formation of Anti-Drug Antibodies Against Cergutuzumab Amunaleukin in Patients with Solid Tumors

PURPOSE

The immunocytokine cergutuzumab amunaleukin (CEA-IL2v) showed manageable safety and favorable pharmacodynamics in phase I/Ib trials in patients with advanced/metastatic carcinoembryonic antigen-positive (CEA+) solid tumors, but this was accompanied by a high incidence of anti-drug antibodies (ADA). We examined B-cell depletion with obinutuzumab as a potential mitigation strategy.

EXPERIMENTAL DESIGN

Preclinical data comparing B-cell depletion with rituximab versus obinutuzumab are summarized. Substudies of phase I/Ib trials investigated the effect of obinutuzumab pretreatment on ADA development, safety, pharmacodynamics, and antitumor activity of CEA-IL2v ± atezolizumab in patients with advanced/metastatic or unresectable CEA+ solid tumors who had progressed on standard of care.

RESULTS

Preclinical data showed superior B-cell depletion with obinutuzumab versus rituximab. In clinical studies, patients received CEA-IL2v monotherapy with (n = 16) or without (n = 6) obinutuzumab pretreatment (monotherapy study), or CEA-IL2v + atezolizumab + obinutuzumab pretreatment (n = 5; combination study). In the monotherapy study, after four cycles (every 2 weeks treatment), 0/15 evaluable patients administered obinutuzumab pretreatment had ADAs versus 4/6 patients without obinutuzumab. Obinutuzumab pretreatment with CEA-IL2v monotherapy showed no new safety signals and pharmacodynamic data suggested minimal impact on T cells and natural killer cells. Conversely, increased liver toxicity was observed in the combination study (CEA-IL2v + atezolizumab + obinutuzumab pretreatment).

CONCLUSIONS

These preliminary findings suggest that obinutuzumab pretreatment before CEA-IL2v administration in patients with CEA+ solid tumors may be a feasible and potent ADA mitigation strategy, with an acceptable safety profile, supporting broader investigation of obinutuzumab pretreatment for ADA mitigation in other settings.

Src/lck inhibitor dasatinib reversibly switches off cytokine release and T cell cytotoxicity following stimulation with T cell bispecific antibodies

Background

T cell engagers are bispecific antibodies recognizing, with one moiety, the CD3ε chain of the T cell receptor and, with the other moiety, specific tumor surface antigens. Crosslinking of CD3 upon simultaneous binding to tumor antigens triggers T cell activation, proliferation and cytokine release, leading to tumor cell killing. Treatment with T cell engagers can be associated with safety liabilities due to on-target on-tumor, on-target off-tumor cytotoxic activity and cytokine release syndrome (CRS). Tyrosine kinases such as SRC, LCK or ZAP70 are involved in downstream signaling pathways after engagement of the T cell receptor and blocking these kinases might serve to abrogate T cell activation when required (online supplemental material 1). Dasatinib was previously identified as a potent kinase inhibitor that switches off CAR T cell functionality.

Methods

Using an in vitro model of target cell killing by human peripheral blood mononuclear cells, we assessed the effects of dasatinib combined with 2+1 T cell bispecific antibodies (TCBs) including CEA-TCB, CD19-TCB or HLA-A2 WT1-TCB on T cell activation, proliferation and target cell killing measured by flow cytometry and cytokine release measured by Luminex. To determine the effective dose of dasatinib, the Incucyte system was used to monitor the kinetics of TCB-mediated target cell killing in the presence of escalating concentrations of dasatinib. Last, the effects of dasatinib were evaluated in vivo in humanized NSG mice co-treated with CD19-TCB. The count of CD20⁺ blood B cells was used as a readout of efficacy of TCB-mediated killing and cytokine levels were measured in the serum.

Results

Dasatinib concentrations above 50 nM prevented cytokine release and switched off-target cell killing, which were subsequently restored on removal of dasatinib. In addition, dasatinib prevented CD19-TCB-mediated B cell depletion in humanized NSG mice. These data confirm that dasatinib can act as a rapid and reversible on/off switch for activated T cells at pharmacologically relevant doses as they are applied in patients according to the label.

Conclusion

Taken together, we provide evidence for the use of dasatinib as a pharmacological on/off switch to mitigate off-tumor toxicities or CRS by T cell bispecific antibodies.

Clinical activity and safety of simlukafusp alfa, an engineered interleukin-2 variant targeted to fibroblast activation protein-α, combined with atezolizumab in patients with recurrent or metastatic cervical cancer

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Background: Simlukafusp alfa (SIM; FAP-IL2v) comprises an interleukin-2 variant (IL-2v) moiety and an antibody against fibroblast activation protein-α (FAP). The binding of SIM to FAP, expressed on cancer-associated fibroblasts, accounts for retention and accumulation in malignant lesions. The engineered IL-2v moiety has an abolished binding to IL-2Rα while the affinity to IL-2Rβγ is retained, resulting in activation of immune effector CD8 T and NK cells, but not of regulatory T cells, and therefore may augment activity of PD-(L)1 inhibitors. Methods: The clinical activity and safety of the SIM and atezolizumab (ATZ) combination in patients with recurrent or metastatic (R/M) cervical squamous cell carcinoma (SCC) were evaluated in a phase 2 basket study (NCT03386721). Patients (pts) were treated with SIM 10 mg IV and ATZ 1200 mg IV once every 3 weeks. The primary endpoint was objective response rate (ORR) by RECIST v1.1 assessed by investigators. Secondary endpoints were: disease control rate (DCR), duration of response (DoR), progression free survival (PFS). Results: 47 Pts with ECOG ≥1 and median age of 53 years (range: 25-69) were enrolled. All pts were checkpoint inhibitor naïve and 40 (85%) had ≥ 1 previous lines of therapy in the metastatic setting. The median number of cycles was 6 (range: 1-29). The ORR was 27% (90% CI: 18, 39) and DCR was 71% (90% CI: 58, 80) in 44 response-evaluable patients: 2 (5%) had complete response, 10 (23%) partial response, and 19 (43%) stable disease. Responses were observed across PD-L1 subgroups (SP142 assay, IC/TC cut-off ≥ 1%) with 8/22 and 4/18 responders in PD-L1+ and PD-L1- patients, respectively. Responses were durable, the median DoR was 13.3 months (95% CI: 7.6, 14.7). PFS probability at 6 months was 0.4 (95% CI: 0.27, 0.59). The most common adverse events (AE) (reported in > 30% patients), irrespective of relatedness to treatment and severity, were pyrexia (74.5%), anemia (48.9%), asthenia (48.9%), AST increased (44.7%), nausea (42.6%), ALT increased (42.6%), vomiting (36.2%) and diarrhea (31.9%). Grade 3 and 4 AEs related to SIM were observed in 63.8 % and 29.8 % of pts, respectively, while serious AEs (SAE) related to SIM were reported in 40.4%. The most common SAEs (reported in > 5% pts) irrespective of relatedness to treatment were infusion related reaction (14.9%), pyrexia (6.4%) and hydronephrosis (6.4%). One Grade 5 event occurred, which was unrelated to treatment. Conclusions: SIM in combination with ATZ demonstrated an acceptable safety profile in pts with R/M cervical SCC. The anti-tumor activity compares favorably to the approved PD-1 inhibitors in this setting and supports further exploration of IL-2v and checkpoint inhibition in this patient population of high unmet medical need. Clinical trial information: NCT03386721.

Randomized phase Ib study to evaluate safety, pharmacokinetics and therapeutic activity of simlukafusp α in combination with atezolizumab ± bevacizumab in patients with unresectable advanced/ metastatic renal cell carcinoma (RCC) (NCT03063762)

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Background: Simlukafusp α ([SIM], FAP-IL2v) is a novel IL-2v immunocytokine engineered to preferentially activate effector CD8 T and NK cells, but not regulatory T cells (Tregs), due to abolished binding to Interleukin-2 receptor α (IL-2Rα) and retained affinity to IL-2Rβγ. High affinity binding of SIM to fibroblast activation protein (FAP), expressed on cancer-associated fibroblasts, mediates its accumulation in malignant lesions. Methods: The Dose-Escalation (DE) consisted of: Arm A: SIM 5-25 mg weekly for 4 weeks, and every 2 weeks (Q2W) thereafter in combination with atezolizumab [ATZ] 840mg Q2W; and Arm B: same as Arm A + bevacizumab [BEV] 10 mg/kg Q2W. Patients (pts) not previously treated were evaluated in the Extension Part: Arm C (n=3): SIM + ATZ every 3 weeks (Q3W); or Arm D (n=25): SIM + ATZ + BEV (“triplet”) Q3W. Primary objectives were: finding the recommended dose of SIM and assessment of objective response rate (ORR) by RECIST v1.1. Results: We enrolled 69 pts with unresectable advanced/ metastatic clear-cell and/or sarcomatoid RCC. Median age of patients was 57 years (range: 35-78). The recommended dose for extension of SIM was 10 mg. Median treatment duration in days in each arm were: A: 106 (range: 1-877); B: 324 (8-940); C: 659 (71-768); D: 437 (1-682). Twenty-five pts are evaluable for therapeutic activity in Arm A [ORR: 24% (6 PR; 90% CI 12.95, 40.12)]; 15 in Arm B [46.7% (1 CR, 6PR; 90% CI 27.67, 66.68)]; 3 in Arm C [33.3% (1PR; 90% CI 7.83, 74.65)]; and 23 in Arm D [47.8% (2 CR, 9 PR; 90% CI 35.74, 68.15)]. Twelve patients are ongoing on study treatment. Treatment related grade 3 and 4 adverse events (AE) occurred respectively in 69.7% and 9.1% patients. The most common serious AEs were pyrexia (10.6 %) and infusion-related reactions (9.1%). 65.2% Of the patients reported at least one AE of elevations in liver transaminases/GGT/ alkaline phosphatase/bilirubin. Drug-related AEs led to dose modification/interruption in 37.9 % of the pts, and treatment discontinuation in 3% of the patients. SIM led to preferential expansion and activation of NK and CD8 T cells (but not Tregs) in peripheral blood and augmented tumor infiltration and tumor inflammation. Intriguingly responses were observed not only in pts with PD-L1 positive or inflamed tumors, but also in pts with PD-L1 negative tumors (n=13) or poorly infiltrated tumors classified as immune deserts (n=2). Conclusions: The combination of SIM with ATZ ± BEV was feasible with an acceptable safety profile. Clinical activity was more favorable for the triplet among the study Arms, but comparable to the ATZ + BEV combination in the IMmotion151 (Rini B, et al 2019). Observed pharmacodynamic findings were consistent with the expected effects. Clinical trial information: NCT03063762.

CD25-Treg-depleting antibodies preserving IL-2 signaling on effector T cells enhance effector activation and antitumor immunity

Intratumoral regulatory T cell (Treg) abundance associates with diminished anti-tumor immunity and poor prognosis in human cancers. Recent work demonstrates that CD25, the high affinity receptor subunit for IL-2, is a selective target for Treg depletion in mouse and human malignancies; however, anti-human CD25 antibodies have failed to deliver clinical responses against solid tumors due to bystander IL-2 receptor signaling blockade on effector T cells, which limits their anti-tumor activity. Here we demonstrate potent single-agent activity of anti-CD25 antibodies optimized to deplete Tregs whilst preserving IL-2-STAT5 signaling on effector T cells, and demonstrate synergy with immune checkpoint blockade in vivo. Pre-clinical evaluation of an anti-human CD25 (RG6292) antibody with equivalent features demonstrates, in both non-human primates and humanized mouse models, efficient Treg depletion with no overt immune-related toxicities. Our data supports the clinical development of RG6292 and evaluation of novel combination therapies incorporating non-IL-2 blocking anti-CD25 antibodies in clinical studies.

Abstract 4553: The CD25 antibody RG6292 selectively depletes Tregs while preserving IL-2 signaling and CTL activity for tumor control

Despite the advances in cancer immunotherapy, in particular in the field of checkpoint inhibitors (CPI), many patients fail to respond (primary resistance) or initially benefit but then progress upon treatment (secondary resistance). High regulatory T-cell (Treg) counts correlate with poor prognosis and reduced responsiveness to CPI therapy in humans, underscoring their potential as an immunotherapy target. Clinical attempts aiming to lower Treg counts, however, either failed to deliver convincing Treg reduction or lacked specificity for Treg over tumor antigen specific cytotoxic T cells (CTL). CD25 (the interleukin-2 receptor alpha (IL-2Ra) chain) is a recently revisited target for Treg depletion. For privileged access to IL-2, activated CTL up-regulate CD25 expression only transiently during clonal expansion. Further confirmation of an &gt; 20 fold higher cell surface expression of CD25 on Tregs versus CTLs in human malignancies is provided. The novel compound RG6292 was developed as an ADCC and ADCP competent monoclonal antibody of human IgG1 isotype with afucosylated glycans in the Fc region. RG6292 binds with low monovalent affinity (KD 250 nM) to the extracellular domain of CD25 antigen. A high density of CD25 receptors promotes bivalent avidity of RG6292 increasing its binding strength to CD25 by at least 100 fold (KD 2-3 nM). RG6292 selectively favors the depletion of CD25 high Tregs over CD25 low activated CTLs, here shown in comparison to ipilimumab and mogamulizumab in human αCD3 activated PBMC, human tumor explants and immunopharmacodynamic studies in tumor bearing (BxPC-3), stem cell humanized mice and cynomolgus monkeys. IL-2 is an essential prerequisite for clonal expansion of CTLs, which is necessary to generate effective anti-tumor responses. Earlier immunosuppressant anti-CD25 antibodies (e.g. daclizumab and basiliximab) interfered with the formation of the high affinity IL-2R complex. Their evidenced lack of therapeutic activity in immunoncology tempered enthusiasm and highlights the pivotal role of IL-2. RG6292 is the first anti-human CD25 antibody developed to deplete Tregs selectively while fully preserving IL-2 signaling and CTL activity. Pre-clinically, a single administration of the RG6292 surrogate effectively promoted eradication of established tumors in several tumor mouse models and synergized with CPI in models of CPI resistance. RG6292 is expected to unleash the potential of selective Treg depletion while allowing for unrestricted access of IL 2 to CTLs and could therefore result in clinically superiority compared to other Treg depleting antibodies. RG6292 provides a novel therapeutic approach to alleviate a major mechanism of immune suppression in the tumor microenvironment. Clinical testing is currently ongoing to evaluate the safety and tolerability of RG6292 in patients with advanced solid tumors (NCT04158583).

Citation Format: Maria Amann, Gabriel Schnetzler, Kolben Theresa, Isabelle Solomon, Christophe Boetsch, Estelle Marrer-Berger, Reto Flury, Claudio Murgia, Vaios Karanikas, Johannes Sam, Roger Sutmuller, Jan Eckmann, Hans Koll, Sara Belli, Frederic Arce Vargas, Dimitrios Zervas, Chen Qing, Mark A. Brown, Josephine Salimu, Anne Goubier, Sebastian Neumann, Karl S. Peggs, Sergio A. Quezada. The CD25 antibody RG6292 selectively depletes Tregs while preserving IL-2 signaling and CTL activity for tumor control [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4553.

Abstract 2270: RG7769 (PD1-TIM3), a novel heterodimeric avidity-driven T cell specific PD-1/TIM-3 bispecific antibody lacking Fc-mediated effector functions for dual checkpoint inhibition to reactivate dysfunctional T cells

Based on the unprecedented clinical efficacy of PD-1/PD-L1 pathway checkpoint inhibitors (CPI), non-redundant immune checkpoints like TIM-3, LAG-3, TIGIT or BTLA are currently being targeted, by combinatorial approaches using monospecific or bispecific antibodies. Up-regulation of TIM-3 has been described as an adaptive CPI resistance mechanism, and internal prevalence data on archival samples of CPI-naïve and -experienced patients showed co-expression of PD-1 and TIM-3 in various tumor types, consistent with literature reports. Here, we describe RG7769 (PD1-TIM3), a novel avidity driven heterodimeric PD-1/TIM-3 1+1 bispecific CrossMabVH-VL intentionally designed as high affinity PD-1 (KD 250 pM, 37°C) and low affinity TIM-3 (KD 130 nM, 37°C) Fab-moieties to specifically target PD-1+ and PD-1+ TIM-3+ T cells through avidity gain, while bypassing PD-1- TIM3+ myeloid and NK cells. In contrast to IgG4-based PD-1 antibodies and conventional IgG1-based TIM-3 Fc-effector function competent antibodies, RG7769 harbors a PG LALA containing heterodimeric KiH IgG1 Fc-region rendering the BsAb refractory to drug shaving by FcgR-expressing macrophages in the TME, while retaining IgG-pharmacokinetics. RG7769 binds to PD-1 with higher affinity than pembrolizumab and nivolumab. X-ray crystallography demonstrated that the humanized PD-1 binding Fab recognizes a unique glycosylated epitope on PD-1, and potently blocks the PD-1/PD-L1 and PD-1/PD-L2 interactions in both biochemical and reporter cell line assays. The humanized TIM-3 binding arm was identified for maximal functional activity using mixed lymphocyte reaction (MLR) assays. Compared with bivalent TIM-3 antibodies, RG7769 shows reduced binding to TIM-3+ myeloid and NK cells, but binds preferentially to dysfunctional T cells expressing PD-1 or both PD-1 and TIM-3, like tumor infiltrating lymphocytes (TILs) in the tumor microenvironment. By virtue of its monovalency, RG7769 induced low antibody internalization on activated T cells when compared with bivalent TIM-3 antibodies, overcoming a major cellular sink for TIM-3 antibodies. In functional assays, RG7769 showed increased IFN-γ secretion by in vitro generated tumor-specific T-cells, increased ex vivo tumor-specific effector functions of T cells from PBMCs of melanoma patients, and enhanced the anti-tumor-activity of TILs from melanoma patients when compared to the monospecific parental PD-1 antibody. Finally, RG7769 showed superior efficacy in controlling s.c. MC38 tumor growth in huPD-1/huTIM-3 transgenic C57/BL6 mice compared to the parental PD-1 antibody. In summary, these preclinical data support the use of RG7769 as a monotherapy and as combination partner for the treatment of patients with solid/hematological tumors. A phase I study is currently ongoing in patients with advanced metastatic solid tumors (NCT03708328).

Citation Format: Laura Laura Codarri Deak, Stefan Seeber, Mario Perro, Patrick Weber, Laura Lauener, Standford Chen, Sonja Offner, Stefan Dengl, Friederike Hesse, Adrian Zwick, Marco Boettger, Alexander Bujotzek, Jörg Benz, Guy Georges, Georg Fertig, Valeria Lifke, Jens Fischer, Stephane Leclair, Victor Levitsky, Marta Canamero, Juha Lindner, Sara Colombetti, Stefanie Bendels, Christophe Boetsch, Matthias Fueth, Merlind Muecke, Henry Kao, Pablo Umana, Christian Klein. RG7769 (PD1-TIM3), a novel heterodimeric avidity-driven T cell specific PD-1/TIM-3 bispecific antibody lacking Fc-mediated effector functions for dual checkpoint inhibition to reactivate dysfunctional T cells [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2270.

The McCAVE Trial: Vanucizumab plus mFOLFOX-6 Versus Bevacizumab plus mFOLFOX-6 in Patients with Previously Untreated Metastatic Colorectal Carcinoma (mCRC)

Background

Bevacizumab, a VEGF‐A inhibitor, in combination with chemotherapy, has proven to increase progression‐free survival (PFS) and overall survival in multiple lines of therapy of metastatic colorectal cancer (mCRC). The angiogenic factor angiopoetin‐2 (Ang‐2) is associated with poor prognosis in many cancers, including mCRC. Preclinical models demonstrate improved activity when inhibiting both VEGF‐A and Ang‐2, suggesting that the dual VEGF‐A and Ang‐2 blocker vanucizumab (RO5520985 or RG‐7221) may improve clinical outcomes. This phase II trial evaluated the efficacy of vanucizumab plus modified (m)FOLFOX‐6 (folinic acid (leucovorin), fluorouracil (5‐FU) and oxaliplatin) versus bevacizumab/mFOLFOX‐6 for first‐line mCRC.

Patients and Methods

All patients received mFOLFOX‐6 and were randomized 1:1 to also receive vanucizumab 2,000 mg or bevacizumab 5 mg/kg every other week. Oxaliplatin was given for eight cycles; other agents were continued until disease progression or unacceptable toxicity for a maximum of 24 months. The primary endpoint was investigator‐assessed PFS.

Results

One hundred eighty‐nine patients were randomized (vanucizumab, n = 94; bevacizumab, n = 95). The number of PFS events was comparable (vanucizumab, n = 39; bevacizumab, n = 43). The hazard ratio was 1.00 (95% confidence interval, 0.64–1.58; p = .98) in a stratified analysis based on number of metastatic sites and region. Objective response rate was 52.1% and 57.9% in the vanucizumab and bevacizumab arm, respectively. Baseline plasma Ang‐2 levels were prognostic in both arms but not predictive for treatment effects on PFS of vanucizumab. The incidence of adverse events of grade ≥3 was similar between treatment arms (83.9% vs. 82.1%); gastrointestinal perforations (10.8% vs. 8.4%) exceeded previously reported rates in this setting. Hypertension and peripheral edema were more frequent in the vanucizumab arm.

Conclusion

Vanucizumab/mFOLFOX‐6 did not improve PFS and was associated with increased rates of antiangiogenic toxicity compared with bevacizumab/mFOLFOX‐6. Our results suggest that Ang‐2 is not a relevant therapeutic target in first‐line mCRC.

Implications for Practice

This randomized phase II study demonstrates that additional angiopoietin‐2 (Ang‐2) inhibition does not result in superior benefit over anti–VEGF‐A blockade alone when each added to standard chemotherapy. Moreover, the performed pharmacokinetic and pharmacodynamic analysis revealed that vanucizumab was bioavailable and affected its intended target, thereby strongly suggesting that Ang‐2 is not a relevant therapeutic target in the clinical setting of treatment‐naïve metastatic colorectal cancer. As a result, the further clinical development of the dual VEGF‐A and Ang‐2 inhibitor vanucizumab was discontinued.

This phase II trial evaluated the efficacy of vanucizumab plus mFOLFOX‐6 versus bevacizumab/mFOLFOX‐6 in the first‐line setting of metastatic colorectal cancer.

Prediction of the Optimal Dosing Regimen Using a Mathematical Model of Tumor Uptake for Immunocytokine-Based Cancer Immunotherapy

Purpose: Optimal dosing is critical for immunocytokine-based cancer immunotherapy to maximize efficacy and minimize toxicity. Cergutuzumab amunaleukin (CEA-IL2v) is a novel CEA-targeted immunocytokine. We set out to develop a mathematical model to predict intratumoral CEA-IL2v concentrations following various systemic dosing intensities.Experimental Design: Sequential measurements of CEA-IL2v plasma concentrations in 74 patients with solid tumors were applied in a series of differential equations to devise a model that also incorporates the peripheral concentrations of IL2 receptor-positive cell populations (i.e., CD8⁺, CD4⁺, NK, and B cells), which affect tumor bioavailability of CEA-IL2v. Imaging data from a subset of 14 patients were subsequently utilized to additionally predict antibody uptake in tumor tissues.Results: We created a pharmacokinetic/pharmacodynamic mathematical model that incorporates the expansion of IL2R-positive target cells at multiple dose levels and different schedules of CEA-IL2v. Model-based prediction of drug levels correlated with the concentration of IL2R-positive cells in the peripheral blood of patients. The pharmacokinetic model was further refined and extended by adding a model of antibody uptake, which is based on drug dose and the biological properties of the tumor. In silico predictions of our model correlated with imaging data and demonstrated that a dose-dense schedule comprising escalating doses and shortened intervals of drug administration can improve intratumoral drug uptake and overcome consumption of CEA-IL2v by the expanding population of IL2R-positive cells.Conclusions: The model presented here allows simulation of individualized treatment plans for optimal dosing and scheduling of immunocytokines for anticancer immunotherapy. Clin Cancer Res; 24(14); 3325-33. ©2018 AACRSee related commentary by Ruiz-Cerdá et al., p. 3236.

First-in-Human Phase I Study of Single-agent Vanucizumab, A First-in-Class Bispecific Anti-Angiopoietin-2/Anti-VEGF-A Antibody, in Adult Patients with Advanced Solid Tumors

Purpose: Vanucizumab is an investigational antiangiogenic, first-in-class, bispecific mAb targeting VEGF-A and angiopoietin-2 (Ang-2). This first-in-human study evaluated the safety, pharmacokinetics, pharmacodynamics, and antitumor activity of vanucizumab in adults with advanced solid tumors refractory to standard therapies.Experimental Design: Patients received escalating biweekly (3-30 mg/kg) or weekly (10-30 mg/kg) intravenous doses guided by a Bayesian logistic regression model with overdose control.Results: Forty-two patients were treated. One dose-limiting toxicity, a fatal pulmonary hemorrhage from a large centrally located mediastinal mass judged possibly related to vanucizumab, occurred with the 19 mg/kg biweekly dose. Arterial hypertension (59.5%), asthenia (42.9%), and headache (31%) were the most common toxicities. Seventeen (41%) patients experienced treatment-related grade ≥3 toxicities. Toxicity was generally higher with weekly than biweekly dosing. A MTD of vanucizumab was not reached in either schedule. Pharmacokinetics were dose-linear with an elimination half-life of 6-9 days. All patients had reduced plasma levels of free VEGF-A and Ang-2; most had reductions in K^TRANS (measured by dynamic contrast-enhanced MRI). Two patients (renal cell and colon cancer) treated with 30 mg/kg achieved confirmed partial responses. Ten patients were without disease progression for ≥6 months. A flat-fixed 2,000 mg biweekly dose (phamacokinetically equivalent to 30 mg/kg biweekly) was recommended for further investigation.Conclusions: Biweekly vanucizumab had an acceptable safety and tolerability profile consistent with single-agent use of selective inhibitors of the VEGF-A and Ang/Tie2 pathway. Vanucizumab modulated its angiogenic targets, impacted tumor vascularity, and demonstrated encouraging antitumor activity in this heterogeneous population. Clin Cancer Res; 24(7); 1536-45. ©2017 AACR.

Effect of molecular mechanisms mediating bevacizumab (BEV) and vanucizumab (VAN) on gastrointestinal perforation: Use of artificial neural networks for integrated data analysis

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Background: VAN is a novel bispecific mAb targeting VEGF & ANG-2. A randomized phase 2 study (McCAVE) investigating VAN & BEV, each combined with chemotherapy (mFOLFOX-6), in 1L metastatic colorectal cancer patients was completed. Reported gastrointestinal perforation (GIP) events (including GI fistula & abdominal abscess) in both arms (approx. 10%) exceeded those expected with BEV+CTx. The present work focused on identifying the explicit molecular pathways mediating VAN/BEV associated GIP. Methods: Clinical data from McCave (safety outcomes & gene expression profiling) was integrated with data from other clinical/preclinical VAN/BEV studies. Machine learning was applied to the dataset to computationally infer GIP mechanisms. The methodology was constrained by relevant biological & clinical knowledge. Literature reviews & database queries mapped 194 unique proteins to 8 biological processes previously hypothesized to play a role in GIP. Identified proteins guided construction of a GIP protein interaction network which was transformed into an artificial neural network and was fitted to the dataset to predict molecular pathways/biological processes most likely linking VEGF-A and/or ANG-2 inhibition to GIP. Results: VAN/BEV were predicted to enhance GIP risk via 4 out of 8 previously suggested biological effects: (i) reduced GI mucosal integrity; (ii) impaired wound healing; (iii) inhibition of angiogenesis (iv) increased thromboembolic risk. The specific proteins & associated interactions predicted to mediate these 4 effects were identified as solely VEGF-A inhibition driven. These effects may drive increased susceptibility to GIP triggered by secondary insults, e.g. preclinical ulcer & intramural lesion. Candidate GIP biomarkers for monitoring these effects were identified, e.g., aPTT, citrulline & I-FABP. Conclusions: The molecular pathways mediating GIP in VAN/BEV treated patients are likely driven by VEGF inhibition with no contribution from ANG-2 inhibition. It is proposed, that in addition to VAN/BEV, one or more secondary insults to the GI tract wall are required to drive perforation.

Modeling Longitudinal Preclinical Tumor Size Data to Identify Transient Dynamics in Tumor Response to Antiangiogenic Drugs

Experimental evidence suggests that antiangiogenic therapy gives rise to a transient window of vessel normalization, within which the efficacy of radiotherapy and chemotherapy may be enhanced. Preclinical experiments that measure components of vessel normalization are invasive and expensive. We have developed a mathematical model of vascular tumor growth from preclinical time‐course data in a breast cancer xenograft model. We used a mixed‐effects approach for model parameterization, leveraging tumor size data to identify a period of enhanced tumor growth that could potentially correspond to the transient window of vessel normalization. We estimated the characteristics of the window for mice treated with an anti‐VEGF antibody (bevacizumab) or with a bispecific anti‐VEGF/anti‐angiopoietin‐2 antibody (vanucizumab). We show how the mathematical model could theoretically be used to predict how to coordinate antiangiogenic therapy with radiotherapy or chemotherapy to maximize therapeutic effect, reducing the need for preclinical experiments that directly measure vessel normalization parameters.

Effects of Cytochrome P450 3A4 Inhibitors-Ketoconazole and Erythromycin-on Bitopertin Pharmacokinetics and Comparison with Physiologically Based Modelling Predictions

OBJECTIVE

To assess the effect of strong and moderate cytochrome P450 (CYP) 3A4 inhibition on exposure of bitopertin, a glycine reuptake inhibitor primarily metabolized by CYP3A4, and to compare the results with predictions based on physiologically based pharmacokinetic (PBPK) modelling.

METHODS

The effects of ketoconazole and erythromycin were assessed in two male volunteer studies with open-label, two-period, fixed-sequence designs. Twelve subjects were enrolled in each of the studies. In period 1, a single dose of bitopertin was administered; in period 2, 400 mg ketoconazole was administered once daily for 17 days or 500 mg erythromycin was administered twice daily for 21 days. A single dose of bitopertin was coadministered on day 5. Pharmacokinetic parameters were derived by non-compartmental methods. Simulated bitopertin profiles using dynamic PBPK modelling for a typical healthy volunteer in GastroPlus(®) were used to predict changes in pharmacokinetic parameters.

RESULTS

In healthy volunteers, coadministration of ketoconazole increased the bitopertin area under the plasma concentration-time curve (AUC) from 0 to 312 h (AUC0-312h) 4.2-fold (90 % confidence interval [CI] 3.5-5.0) and erythromycin increased the AUC from time zero to infinity (AUC0-inf) 2.1-fold (90 % CI 1.9-2.3). The peak concentration (C max) increased by <25 % in both studies. Simulated bitopertin profiles using PBPK modelling showed good agreement with the observed AUC ratios in both studies. The predicted AUC0-inf ratios for the interaction with ketoconazole and erythromycin were 7.7 and 1.9, respectively.

CONCLUSION

Strong CYP3A4 inhibitors increase AUC0-inf of bitopertin 7- to 8-fold and hence should not be administered concomitantly with bitopertin. Moderate CYP3A4 inhibitors double AUC0-inf.

Physiologically based absorption modelling to predict the impact of drug properties on pharmacokinetics of bitopertin

Bitopertin (RG1678) is a glycine reuptake inhibitor in phase 3 trials for treatment of schizophrenia. Its clinical oral pharmacokinetics is sensitive to changes in drug substance particle size and dosage form. Physiologically based pharmacokinetic (PBPK) absorption model simulations of the impact of changes in particle size and dosage form (either capsules, tablets, or an aqueous suspension) on oral pharmacokinetics was verified by comparison to measured plasma concentrations. Then, a model parameter sensitivity analysis was applied to set limits on the particle sizes included in tablets for the market. The model was also used to explore the in vitro to in vivo correlation. Simulated changes in oral pharmacokinetics caused by differences in particle size and dosage form were confirmed in two separate relative bioavailability studies. Model parameter sensitivity analyses predicted that AUCinf was hardly reduced as long as particle diameter (D50) remained smaller than 30 μm, and >20% reduced Cmax is anticipated only when particle diameter exceeds 15 μm. An exploration of the sensitivity to the presence of larger particles within a polydisperse distribution showed that simulated Cmax is again more affected than AUC but is less than 20% reduced as long as D50 is less than 8 μm and D90 is smaller than 56 μm. PBPK absorption modelling can contribute to a quality by design (QbD) approach for clinical formulation development and support the setting of biorelevant specifications for release of the product.