Triplet regimens leveraging novel agents targeted at overcoming mechanisms of resistance in combination with immune checkpoint inhibitors and anti-angiogenic therapies represent the next frontier in hepatocellular carcinoma.
Investigators are exploring many promising hypotheses to target mechanisms of intrinsic and extrinsic resistance to immune checkpoint inhibitors (ICIs) to advance care for patients with hepatocellular carcinoma (HCC). Triplet regimens leveraging novel agents targeted at overcoming mechanisms of resistance in combination with ICIs and anti-angiogenic therapies represent the next frontier, according to Robin Kate Kelley, MD, who presented an overview of the treatment landscape during the 2021 International Liver Cancer Association Conference.1
“There’s enormous clinical need for new therapies and combinations post ICI progression,” said Kelley, a gastrointestinal oncologist and a professor of clinical medicine in the Division of Hematology/Oncology at the Helen Diller Family Comprehensive Cancer Center at the University of California, San Francisco. “We should be studying the mechanisms of resistance [in] the first line and later lines.”
The rationale for exploring triplet combinations to overcome resistance stems from the success demonstrated in data from approved and exploratory ICI combinations. “The primary goal is synergy,” Kelley said. “[We want to] automate rates of response by targeting mechanisms of primary tumor intrinsic or extrinsic resistance and [either] delay progression or prolong response by targeting acquired resistance.” A secondary goal of triplet therapies is to elicit an additive benefit, added Kelley, noting these patients have a very limited window of opportunity nutrition between lines of therapy.
With the role of expanding systemic therapies, investigators of triplet regimens will use the proven efficacy demonstrated with ICI combinations in HCC as building blocks. This includes the combination of atezolizumab (Tecentriq) plus bevacizumab (Avastin), which was approved by the FDA in May 2020 for the treatment of patients with unresectable or metastatic hepatocellular carcinoma who have not received prior systemic therapy based on data from the phase 3 IMbrave150 trial (NCT03434379).2
“[In] the advanced space, the first-line combination of atezolizumab plus bevacizumab has emerged as the global standard of care,” Kelley said. “The combination of [an ICI] plus an anti-angiogenic agent is based on the rationale that targeting VEGF inhibits the regulatory and suppressive elements of the immune microenvironment, [such as] Tregs, myeloid derived suppressor cells, and tumor-associated macrophages, relieving the inhibition of the immune activating elements, such as effector T cells and antigen presentation.”
Data are being reported out for other ongoing trials in the first line setting. For example, the combination of atezolizumab and the TKI cabozantinib (Cabometyx) demonstrated significant improvement in progression-free survival (PFS), meeting the primary end point of the phase 3 COSMIC-312 trial (NCT03755791).3 Randomized phase 3 trials are underway for combinations including pembrolizumab (Keytruda) plus lenvatinib (Lenvima) in LEAP-002 (NCT03713593); nivolumab (Opdivo) plus ipilimumab (Yervoy) vs sorafenib (Nexavar) or lenvatinib in CheckMate 9DW (NCT04039607); and durvalumab (Imfinzi) plus tremelimumab vs sorafenib in HIMALAYA (NCT03298451).1
ICI doublets lay the groundwork for investigators, but the identification and targeting of resistance mechanisms provide the direction. “There are many promising hypotheses about how to address resistance, and these are being tested in triplet therapies and signal finding clinical trials,” Kelley said. “The predominant [targets] include mechanisms of both intrinsic and extrinsic resistance.”
Tumor intrinsic factors include insufficient antigenicity or lack of neoantigens, defects in the interferon-γ signaling, loss of major histocompatibility complex, and oncogenic signaling escape mechanisms. Tumor extrinsic factors such as the absence of T cells in the tumor microenvironment and the presence of immune suppressive cells, such as Tregs, contribute to resistances as well.1
The predominant way that investigators are exploring the efficacy of triplet combinations in clinical trials is combining immune checkpoint inhibitors with liver directed therapies, Kelley said. There are several alternative methods under investigation as well, Kelley noted, including targeting alternative new checkpoint inhibitor pathways, myeloid activation pathways and oncogenic signaling pathways.
The combination platform study, Morpheus-Liver (NCT04524871), is one such trial that is evaluating the safety and efficacy of multiple immunotherapy-based treatment combinations. “[Investigators of the] study are looking at the combination of atezolizumab plus bevacizumab as a backbone [therapy] with multiple different immune-modulatory or -inhibitory approaches to help promote an immune response to the [combination,” Kelley explained.
One arm of the trial is evaluating tiragolumab, a monoclonal antibody designed to bind with TIGIT, an inhibitory receptor that is associated with poor clinical outcomes for patients with advanced HCC. The agent has demonstrated activity with atezolizumab in patients with non–small cell lung cancer with high PD-L1 expression (tumor proportion score ≥ 50%).1,4
LAG-3 is another target under investigation in the Morpheus-Liver study. Investigators are evaluating the efficacy of the novel anti-PD-1/anti-LAG-3 bispecific antibody RO7247669. The rationale for use of this agent comes from demonstrated efficacy of targeting LAG-3 as an alternative to PD-1/PD-L1 or CTLA4 in patients with melanoma.1,5,6
Moving into suppression of myeloid pathways, Kelley called attention to interleukin 6 (IL-6). “We know that myeloid pathways and myeloid inflammation can be pro-tumorigenic as well as immune suppressive,” Kelley said. Investigators of the Morpheus-Liver study have included an arm to explore the role of targeting IL-6 with tocilizumab (Actemra).1 Although rather limited data exist for the agent in this setting Kelley said that it is “a very interesting mechanism for utility in this malignancy.”
Investigators of the Morpheus-Liver study are also assessing the role of suppressing oncogenic signaling pathways, specifically PPRα, which mediates fatty acid oxidation. Patients with HCC typically have high expression of fatty acid oxidation genes compared with other tumor types, according to Kelley, who noted that this “provocative finding” suggests a role for TPST-1120, a novel PPRα inhibitor, in HCC. The agent has demonstrated synergy with anti-PD1 in HCC cell lines.1
Outside of the Morpheus-Liver study, investigators are examining the oncogenic signaling pathway hypoxia inducible factor (HIF)-2α, which is upregulated by sorafenib and is associated with tyrosine kinase inhibitor (TKI) resistance. Belzutifan (Welireg), a HIF-2α inhibitor, is being investigated in a phase 2 basket trial (NCT04976634) in combination with pembrolizumab and lenvatinib in patients with multiple solid tumors including HCC.1
Finally, Kelley discussed the efficacy of multikinase inhibitors with or without CTLA-4 inhibition in overcoming ICI/TKI resistance. Specifically, she turned to data from a cohort of the ongoing CheckMate040 trial (NCT01658878). The trial enrolled patients with advanced HCC who had not received prior sorafenib or whom had progressed or were intolerant to sorafenib.
Investigators compared nivolumab plus ipilimumab plus cabozantinib (n = 35) or nivolumab plus ipilimumab (n = 36). The investigator-assessed objective response rate was 29% in the triplet arm compared with 19% in the doublet arm.7 The disease control rates were 83% vs 75%, respectively. The median PFS was 6.8 months (95% CI, 4.0-14.3) in the triplet arm compared with 5.4 months (95% CI, 3.2-10.9) in the doublet arm. Further, the median overall survival (OS) was not reached (NR) in the triplet arm (95% CI, 15.1-NR) vs 21.5 months (13.1-NR) in the doublet arm; the 15-month OS rates were 70% (95% CI, 51%-83%) vs 64% (95% CI, 45%-78%), respectively.7 Of note the rate of grade 3/4 adverse effects were higher with the triplet (71%) than the doublet (47%).
“Early data from [CheckMate040] showed nivolumab plus ipilimumab plus cabozantinib suggests the potential for higher response rate with a triplet, but also higher rates of grade 3 to 4 toxicity,” Kelley said.
Kelley highlighted another tumor-extrinsic mechanism of ICI resistance in HCC of interest—nonalcoholic steatohepatitis (NASH), which has emerged as risk factor for patients. In HCC mouse models, treatment with anti-PD1 therapies was associated with an increase in NASH-driven HCC. In a meta-analysis of patients with HCC who received PD-1/PD-L1 therapy, results showed that those with NASH-driven HCC had inferior improvements in OS.8
Oncolytic viruses are another intriguing way to promote tumor immunogenicity and address intrinsic resistance, Kelley said. However, investigative efforts exploring the use of this strategy are early and no data was available for discussion at the time of the presentation.
Despite the identification of resistance mechanisms and early efficacy seen with triplet regimens, Kelley noted that challenges are abound in determining the optimal role for these treatments, such as discerning synergy vs the sum of component parts. Investigators need to determine if a third agent is eliciting a truly synergistic effect rather than providing an “a purely additive effect,” Kelley said. “We need randomized, well-stratified, and adequately powered studies to validate single-arm study signals, ideally compared to the pertinent doublets,” she said.
Another challenge Kelley noted is that mechanisms of resistance and synergy effects may be context dependent. “This requires us to conduct exquisite correlative analysis of blood and tissue [samples] to look [for] pharmacodynamic markers,” Kelley said. Investigators can then use these markers to match clinical end points, as well as to identify biomarkers that will aid in the identification of subpopulations that may benefit or not benefit from triplet therapy.
Key clinical considerations include the potential of overlapping and cumulative toxicities, cost, and complexity. Additionally, decision-making regarding combined vs sequential therapy will require a deeper understanding of mechanisms of resistance.
The future of multiagent ICI combinations is not without hope, according to Kelley, who provided an outline for future first, second, and later study designs. First-line triplet ICI combination studies should recapitulate the IMbrave150 population closely and require that archival or fresh tumor and tissue samples, as well as serial blood samples, be collected from all patients in all phases. Further, serologic annotation for hepatitis B and hepatitis C and clinical annotation for nonalcoholic fatty liver disease, risk factors, and antiviral therapy status should be collected.
Across lines of therapy, Kelley said that the efforts need to be intensified to identify subpopulations for individual combinations based on resistance mechanisms using biomarker and cohort analyses. “We will need to use these reported outcomes and quality of life analysis to help contextualize the efficacy signal,” she concluded.