Phase I Study of Safety, Tolerability, and Efficacy of Tebentafusp Using a Step-Up Dosing Regimen and Expansion in Patients With Metastatic Uveal Melanoma

PURPOSE

This phase I study aimed to define the recommended phase II dose (RP2D) of tebentafusp, a first-in-class T-cell receptor/anti-CD3 bispecific protein, using a three-week step-up dosing regimen, and to assess its safety, pharmacokinetics, pharmacodynamics, and preliminary clinical activity in patients with metastatic uveal melanoma (mUM).

METHODS

In this open-label, international, phase I/II study, HLA-A*02 or HLA-A*02:01+ patients with mUM received tebentafusp 20 μg once in week 1 and 30 μg once in week 2. Dose escalation (starting at 54 μg) began at week 3 in a standard 3 + 3 design to define RP2D. Expansion-phase patients were treated at the RP2D (20-30-68 μg). Blood and tumor samples were collected for pharmacokinetics/pharmacodynamics assessment, and treatment efficacy was evaluated for all patients with baseline efficacy data as of December 2017.

RESULTS

Between March 2016 and December 2017, 42 eligible patients who failed a median of two previous treatments were enrolled: 19 in the dose escalation cohort and 23 in an initial dose expansion cohort. Of the dose levels investigated, 68 μg was identified as the RP2D. Most frequent treatment-emergent adverse events regardless of attribution were pyrexia (91%), rash (83%), pruritus (83%), nausea (74%), fatigue (71%), and chills (69%). Toxicity attenuated following the first three doses. The overall response rate was 11.9% (95% CI, 4.0 to 25.6). With a median follow-up of 32.4 months, median overall survival was 25.5 months (range, 0.89-31.1 months) and 1-year overall survival rate was 67%. Treatment was associated with increased tumor T-cell infiltration and transient increases in serum inflammatory mediators.

CONCLUSION

Using a step-up dosing regimen of tebentafusp allowed a 36% increase in the RP2D compared with weekly fixed dosing, with a manageable side-effect profile and a signal of efficacy in mUM.

Clinical and molecular response to tebentafusp in previously treated patients with metastatic uveal melanoma: a phase 2 trial

In patients with previously treated metastatic uveal melanoma, the historical 1 year overall survival rate is 37% with a median overall survival of 7.8 months. We conducted a multicenter, single-arm, open-label phase 2 study of tebentafusp, a soluble T cell receptor bispecific (gp100×CD3), in 127 patients with treatment-refractory metastatic uveal melanoma (NCT02570308). The primary endpoint was the estimation of objective response rate based on RECIST (Response Evaluation Criteria in Solid Tumours) v1.1. Secondary objectives included safety, overall survival, progression-free survival and disease control rate. All patients had at least one treatment-related adverse event, with rash (87%), pyrexia (80%) and pruritus (67%) being the most common. Toxicity was mostly mild to moderate in severity but was greatly reduced in incidence and intensity after the initial three doses. Despite a low overall response rate of 5% (95% CI: 2-10%), the 1 year overall survival rate was 62% (95% CI: 53-70%) with a median overall survival of 16.8 months (95% CI: 12.9-21.3), suggesting benefit beyond traditional radiographic-based response criteria. In an exploratory analysis, early on-treatment reduction in circulating tumour DNA was strongly associated with overall survival, even in patients with radiographic progression. Our findings indicate that tebentafusp has promising clinical activity with an acceptable safety profile in patients with previously treated metastatic uveal melanoma, and data suggesting ctDNA as an early indicator of clinical benefit from tebentafusp need confirmation in a randomized trial.

Overall Survival Benefit with Tebentafusp in Metastatic Uveal Melanoma

BACKGROUND

Uveal melanoma is a disease that is distinct from cutaneous melanoma, with a low tumor mutational burden and a 1-year overall survival of approximately 50% in patients with metastatic uveal melanoma. Data showing a proven overall survival benefit with a systemic treatment are lacking. Tebentafusp is a bispecific protein consisting of an affinity-enhanced T-cell receptor fused to an anti-CD3 effector that can redirect T cells to target glycoprotein 100-positive cells.

METHODS

In this open-label, phase 3 trial, we randomly assigned previously untreated HLA-A*02:01-positive patients with metastatic uveal melanoma in a 2:1 ratio to receive tebentafusp (tebentafusp group) or the investigator's choice of therapy with single-agent pembrolizumab, ipilimumab, or dacarbazine (control group), stratified according to the lactate dehydrogenase level. The primary end point was overall survival.

RESULTS

A total of 378 patients were randomly assigned to either the tebentafusp group (252 patients) or the control group (126 patients). Overall survival at 1 year was 73% in the tebentafusp group and 59% in the control group (hazard ratio for death, 0.51; 95% confidence interval [CI], 0.37 to 0.71; P<0.001) in the intention-to-treat population. Progression-free survival was also significantly higher in the tebentafusp group than in the control group (31% vs. 19% at 6 months; hazard ratio for disease progression or death, 0.73; 95% CI, 0.58 to 0.94; P = 0.01). The most common treatment-related adverse events in the tebentafusp group were cytokine-mediated events (due to T-cell activation) and skin-related events (due to glycoprotein 100-positive melanocytes), including rash (83%), pyrexia (76%), and pruritus (69%). These adverse events decreased in incidence and severity after the first three or four doses and infrequently led to discontinuation of the trial treatment (2%). No treatment-related deaths were reported.

CONCLUSIONS

Treatment with tebentafusp resulted in longer overall survival than the control therapy among previously untreated patients with metastatic uveal melanoma. (Funded by Immunocore; ClinicalTrials.gov number, NCT03070392; EudraCT number, 2015-003153-18.).

Resistance to durvalumab and durvalumab plus tremelimumab is associated with functional STK11 mutations in non-small-cell lung cancer patients and is reversed by STAT3 knockdown

Mutations in the STK11 (LKB1) gene regulate resistance to PD-1/PD-L1 blockade. This study evaluated this association in patients with nonsquamous non-small-cell lung cancer enrolled in three Phase 1/2 trials. STK11 mutations were associated with resistance to the anti-PD-L1 antibody durvalumab (alone/with the anti-CTLA-4 antibody tremelimumab) independently of KRAS mutational status, highlighting STK11 as a potential driver of resistance to checkpoint blockade. Retrospective assessments of tumor tissue, whole blood and serum revealed a unique immune phenotype in patients with STK11 mutations, with increased expression of markers associated with neutrophils (i.e. CXCL2, IL6), Th17 contexture (i.e. IL17A) and immune checkpoints. Associated changes were observed in the periphery. Reduction of STAT3 in the tumor microenvironment using an antisense oligonucleotide reversed immunotherapy resistance in preclinical STK11 knockout models. These results suggest that STK11 mutations may hinder response to checkpoint blockade through mechanisms including suppressive myeloid cell biology, which could be reversed by STAT3-targeted therapy.

Abstract CT038: Kinetics of radiographic response for tebentafusp (tebe) in previously treated metastatic uveal melanoma (mUM) patients (pts) achieving prolonged survival

Background: The phase 3 IMCgp100-202 trial (NCT03070392) (Study 202) in untreated mUM demonstrated improved overall survival (OS), HR=0.51, at the first pre-specified interim analysis. This OS benefit and the promising estimated 12-month OS rate of 62% observed in previously treated mUM pts on the phase 2 IMCgp100-102 trial (Study 102; NCT02570308) is not explained by RECIST responses alone. In this post hoc analysis of Study 102, we describe the tumor kinetics of pts with prolonged survival (OS ≥ 12 mo).

Methods: 127 pts with 2L+ mUM received single agent tebe during the expansion phase of Study 102, where treatment beyond RECIST progression was permitted. Analyses of baseline (BL) and on-treatment tumor measurements, best response and time to progression used in this analysis were adjudicated by an independent radiologic committee.

Results: With 19.5 mo median follow-up, 59% (75/127) of pts had OS ≥ 12 mo. Of these 75, a minority had RECIST partial response (PR: 8%; 6/75) and the rest had a best response of stable disease (SD: 57%; 43/75), progressive disease (PD: 33%; 25/75), or not evaluable (NE: 1%; 1/75). In contrast, among 41% (52/127) of pts with OS &lt; 12 mo, 27% (14/52) had SD, 67% (35/52) had PD, and 6% were NE (3/52) as best response. Pts with OS ≥ 12 mo were more likely to have a largest liver metastasis of &lt; 3 cm (43% vs 23%). There were no major differences in the use of prior immunotherapy between the two OS groups.

Most pts with OS ≥ 12 mo (59%; 44/75) had at least some reduction in the sum of target lesions, regardless of RECIST response. The majority of these 44 pts (64%; 28/44) had durable tumor reduction defined by PFS &gt; 6 mo. In contrast, among OS &lt; 12 mo pts, reduction in the sum of target lesions was infrequent (13%; 7/52), and none were durable.

Most pts with tumor growth as best change in target lesions had OS &lt;12 mo (58%; 38/65) compared to OS ≥ 12 mo (42%; 27/65). Among pts with tumor growth, the median BL tumor burden was lower and the rate of increase over time was slower for pts with OS ≥ 12 mo (BL: 59 mm, W8: 68 mm, W16: 68 mm) compared to pts with OS &lt; 12 mo (BL: 113 mm, W8: 129 mm, W16: 143 mm).

Interestingly, 42% (25/60) of pts with best response of PD had OS ≥ 12 mo including 4 pts with evidence of tumor shrinkage at 6 months or later. The reason for PD (new lesions or growth in index lesions) was comparable between both OS groups. More pts continued treatment beyond progression in the OS ≥ 12 (81%) compared to OS &lt; 12 mo (56%).

Conclusion: Analysis of tumor kinetics while on tebe, the first TCR bispecific to report an OS benefit in a solid tumor, suggests most pts with OS ≥ 12 mo are best described by a new type of immune-related response characterized by durable tumor reduction and slowing rate of tumor growth. RECIST responses therefore capture a minority of patients with OS ≥ 12 mo, while just under half of pts with RECIST PD still had promising OS.

Citation Format: Marcus O. Butler, Takami Sato, Richard D. Carvajal, Joseph J. Sacco, Shaad E. Abdullah, Chris Holland, Howard Goodall, Alexander N. Shoushtari. Kinetics of radiographic response for tebentafusp (tebe) in previously treated metastatic uveal melanoma (mUM) patients (pts) achieving prolonged survival [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr CT038.

Abstract CT002: Phase 3 randomized trial comparing tebentafusp with investigator's choice in first line metastatic uveal melanoma

Background: Metastatic uveal melanoma (mUM) has a poor prognosis with a 1-yr OS rate of 52%. No systemic treatment has proven an OS benefit in randomized trials. Tebentafusp (tebe), a bispecific consisting of an affinity-enhanced T cell receptor (TCR) fused to an anti-CD3 effector that can redirect T cells to target gp100+ cells, has shown promising activity in previously treated mUM pts. Here, we report the primary analysis of overall survival (OS) in the intention-to-treat population (ITT) of a Ph3 trial of tebe vs. investigator's choice (IC) as first line (1L) therapy in pts with mUM [NCT03070392].

Materials and Methods: In this randomized, open-label, Ph3 trial, 1L HLA-A*02:01+ pts with mUM were randomized 2:1 to receive tebe or IC of pembrolizumab, ipilimumab or dacarbazine, stratified by LDH. The primary endpoint was OS, defined as the time from randomization to death from any cause. Dual primary objectives were to evaluate 1) OS in the ITT population by comparing all tebe-randomized pts to all IC-randomized pts; and 2) OS in tebentafusp-treated patients with rash during week 1 versus all IC-treated patients. Secondary endpoints included safety and RECIST-defined overall response rate (ORR), progression free survival (PFS) and disease control rate (DCR). Here we present the OS in the ITT population. The study was unblinded by an independent data monitoring committee at the first pre-specified interim analysis. Investigator-reported radiographic-based endpoints were not mature at the first interim analysis. This analysis was conducted on the first interim analysis (data extracted Nov 2020).

Results: 378 pts were randomized to tebe (252) or IC, including pembrolizumab (103), ipilimumab (15) or dacarbazine (7). Tebe significantly prolonged OS compared to IC (HR 0.51; 95% CI 0.36-0.71; P&lt;0.0001) in the ITT population, with estimated 1-yr OS rate of 73.2% (95% CI 66.3-78.9) vs 57.5% (95% CI 47.0-66.6), respectively. The OS benefit of tebe was observed in pre-specified subgroups, including by stratification variable of LDH&gt;ULN and versus pembrolizumab IC. Most common TRAEs were skin-related (gp100+ melanocytes) or cytokine-mediated (T cell activation) and included pyrexia, pruritus, and rash. These AEs decreased in frequency and severity after the first 3-4 doses and were generally manageable with standard interventions. In the tebe arm, the rate of treatment discontinuation due to TRAEs was low (&lt;4%), and there were no treatment-related deaths.

Conclusions: In 1L treatment of mUM pts, tebe monotherapy significantly improved OS compared to IC; the first investigational therapy to improve OS in pts with mUM. Tebe had a predictable and manageable AE profile with a low rate of related discontinuation. Tebe is the first TCR therapeutic to demonstrate an OS benefit.

Citation Format: Sophie Piperno-Neumann, Jessica C. Hassel, Piotr Rutkowski, Jean-Francois Baurain, Marcus O. Butler, Max Schlaak, Ryan J. Sullivan, Sebastian Ochsenreither, Reinhard Dummer, John M. Kirkwood, Anthony M. Joshua, Joseph J. Sacco, Alexander N. Shoushtari, Marlana Orloff, Richard D. Carvajal, Omid Hamid, Shaad E. Abdullah, Chris Holland, Howard Goodall, Paul Nathan. Phase 3 randomized trial comparing tebentafusp with investigator's choice in first line metastatic uveal melanoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr CT002.

Prognostic and Predictive Impact of Circulating Tumor DNA in Patients with Advanced Cancers Treated with Immune Checkpoint Blockade

The utility of circulating tumor DNA (ctDNA) as a biomarker in patients with advanced cancers receiving immunotherapy is uncertain. We therefore analyzed pretreatment (n = 978) and on-treatment (n = 171) ctDNA samples across 16 advanced-stage tumor types from three phase I/II trials of durvalumab (± the anti-CTLA4 therapy tremelimumab). Higher pretreatment variant allele frequencies (VAF) were associated with poorer overall survival (OS) and other known prognostic factors, but not objective response, suggesting a prognostic role for patient outcomes. On-treatment reductions in VAF and lower on-treatment VAF were independently associated with longer progression-free survival and OS and increased objective response rate, but not prognostic variables, suggesting that on-treatment ctDNA dynamics are predictive of benefit from immune checkpoint blockade. Accordingly, we propose a concept of "molecular response" using ctDNA, incorporating both pretreatment and on-treatment VAF, that predicted long-term survival similarly to initial radiologic response while also permitting early differentiation of responders among patients with initially radiologically stable disease. SIGNIFICANCE: In a pan-cancer analysis of immune checkpoint blockade, pretreatment ctDNA levels appeared prognostic and on-treatment dynamics predictive. A "molecular response" metric identified long-term responders and adjudicated benefit among patients with initially radiologically stable disease. Changes in ctDNA may be more dynamic than radiographic changes and could complement existing trial endpoints.This article is highlighted in the In This Issue feature, p. 1775.

Abstract 3295: Vitiligo and other clinical melanocyte-related adverse events following tebentafusp (IMCgp100) exposure in patients with uveal melanoma

Background

Tebentafusp, a TCR-anti-CD3 bispecific fusion protein designed to target a peptide from melanocyte lineage antigen gp100, has shown monotherapy activity in advanced cutaneous and uveal melanoma (UM) [1]. gp100 is expressed in normal melanocytes in skin and hair follicles. We previously reported a possible association between rash and overall survival (OS) in a Ph 1/2 trial of HLA-A*0201 patients with UM [1]. Anti-PD1 therapy for melanoma can induce vitiligo in 10-25% of patients, with one study showing a median time to onset of 126 days (range 52 - 453) and a potential association with clinical benefit [2]. We now investigate the association of melanocyte-related adverse events (MRAEs) and OS following tebentafusp treatment of patients with UM.

Methods

To test the differential potency of tebentafusp, HLA-A2+ epidermal skin derived melanocytes (5 healthy donors) and gp100+ and gp100- melanoma cell lines were incubated with PBMCs and increasing tebentafusp concentrations, and tested in IFNγ (measure of T cell activation) and GrB (measure of T cell mediated killing) ELISPOT assays. The clinical trial database (NCT02570308; Ph1 n=19, Ph2 n=23) was also queried for AEs suggestive of melanocyte origin, including vitiligo, leukotrichia, and skin hyperpigmentation. Simon-Makuch estimates were derived to visualize the association between MRAEs and OS while adjusting for immortal time bias, and Mantel-Byar method was used to estimate odds of death associated with experiencing MRAEs.

Results

In vitro, tebentafusp redirected and activated T cells against gp100+ melanoma and skin-derived melanocytes but not gp100- melanoma; in all cases, potency for melanocytes was less than melanoma, potentially reflecting differential peptide presentation. 24 of 42 patients (57%) developed one or more MRAEs including vitiligo/skin hypopigmentation (28%), leukotrichia (33%), and hyperpigmentation (21%), with median time to onset of 67 days (range 24-221). The estimated probability of experiencing a MRAE within 6-months of continuous treatment is 70%. Among the 24 patients with MRAEs, 22 (92%) and 20 (83%) experienced rash and pruritus, respectively. Rash preceded MRAEs in all patients with both events, while pruritus preceded MRAEs in 77% of patients. In a post-hoc analysis, experiencing a MRAE was associated with a 72% lower odds of death compared to those who did not experience these AEs.

Conclusion

Over half of tebentafusp-treated patients with advanced UM experienced at least one MRAE, supporting the hypothesis that tebentafusp can redirect T cells against gp100+ cells in patients. This rate of MRAEs is higher than historically reported for anti-PD1 based therapies. MRAEs appear to be associated with prior rash, and even accounting for the time bias of onset, may be associated with OS.

1. Sato T. J Clin Oncol 36, 2018, suppl, 9521

2. Hua C. JAMA Dermatol 2016;152:45-51

Citation Format: Marlana Orloff, Joseph J. Sacco, Paul Nathan, Chris Holland, Chris Cohen, Jane Harper, Shaad E. Abdullah, Takami Sato, Richard D. Carvajal. Vitiligo and other clinical melanocyte-related adverse events following tebentafusp (IMCgp100) exposure in patients with uveal melanoma [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 3295.

Dermatologic Toxicities from Monoclonal Antibodies and Tyrosine Kinase Inhibitors against EGFR: Pathophysiology and Management

Epidermal growth factor receptor (EGFR) inhibition has now been well established as an effective treatment for various cancers. The EGFR belongs to the ErbB family of tyrosine kinase receptors which regulate tumor cell differentiation, survival and proliferation. Activation of EGFR drives tumorigenesis in lung, head and neck, colorectal and pancreatic cancers. Irrespective of the type of cancer being treated and the mechanism by which tumor EGFR drives tumorigenesis, the major side effect of EGFR inhibition is a papulopustular (also described as maculopapular or acneiform) rash which occurs in about two thirds of treated patients. Interestingly, this rash has been commonly correlated with better clinical outcomes (objective tumor response and patient survival). The pathophysiology of dermatological toxicity from EGFR inhibitors is an important area of clinical research, and the proper management of the rash is essential to increase the therapeutic index from this class of drugs. In this paper, we review the dermatologic toxicities associated with EGFR inhibitors with an emphasis on its pathophysiology and clinical management.

Mechanisms of resistance to vascular endothelial growth factor blockade

Angiogenesis is essential for the growth of primary tumors and for their metastasis. This process is induced by factors, such as vascular endothelial growth factors (VEGFs), that bind to transmembrane VEGF receptors (VEGFRs). VEGF-A is the primary factor involved with angiogenesis; it binds to both VEGFR-1 and VEGFR-2. The inhibition of angiogenesis by obstructing VEGF-A signaling has been investigated as a method to treat solid tumors, but the development of resistance to this blockade has complicated treatment. The major mechanisms of this resistance to VEGF-A blockade include signaling by redundant receptors, such as the fibroblast growth factors, angiopoietin-1, ephrins, and other forms of VEGF. Other major mechanisms of resistance are increased metastasis of hypoxia-resistant tumor cells, recruitment of cell types capable of promoting VEGF-independent angiogenesis, and increased circulation of nontumor proangiogenic factors. Additional mechanisms of resistance to VEGF-A blockade include heterogeneity of responsiveness among tumor cells, use of anti-VEGF-A agents at insufficient doses or for insufficient duration, altered sensitivity to anti-VEGF-A agents by mutations in endothelial cells or vascular remodeling, maintenance of vascular sleeves that allow for easy regrowth of tumor vasculature upon discontinuation of therapy, vascular cooption, and intussusceptive angiogenesis. An understanding of these mechanisms may lead to the development of targeted therapies that overcome this resistance. Some of these approaches include the combined inhibition of redundant angiogenic pathways, proper patient selection for various therapies based on gene expression profiles, blockade of cellular migration by inhibition of colony-stimulating factor, or the use of agents to disrupt vascular architecture.