Targeted Therapies for Hepatocellular Carcinoma Treatment

Abstract

Hepatocellular carcinoma (HCC) ranks among the most prevalent cancers globally, claiming the third spot in cancer-related fatalities. Surgery stands out as the optimal prognostic measure. Notable factors contributing to HCC encompass chronic viral infections, specifically hepatitis B virus (HBV) and hepatitis C virus (HCV), aflatoxins, tobacco use, and non-alcoholic fatty liver disease (NAFLD). The imperative task at hand is the creation of effective molecular markers and alternative therapeutic targets of substantial importance. This chapter delves into the overarching characteristics of HCC, offering insights into various targeted therapies that have propelled advancements in HCC treatment, underscoring the critical need for ongoing developments in this direction.

1. Introduction

Hepatocellular carcinoma (HCC) stands out as the predominant primary liver malignancy globally, presenting a significant health challenge, particularly in sub-Saharan African and Asian nations. It ranks as the fifth most common cancer diagnosis in males and the sixth in females, causing 250,000–1,000,000 deaths globally. The incidence of liver cancer exhibits considerable geographical variation. Extensive research has outlined the causative factors of HCC, including chronic hepatitis B virus (HBV), chronic hepatitis C virus (HCV), liver cirrhosis, non-alcoholic fatty liver disease (NAFLD), tobacco smoking, and consumption of aflatoxin rich foods. Notably, a higher incidence is observed in males due to the prevalence of chronic viral liver infections, tobacco smoking, and heavy alcohol consumption. Investigations are ongoing regarding the potential protective role of estrogens [1]. Orthotopic liver transplantation (OLT) is the favored treatment for terminal-stage patients, boasting 1-year survival rates of 80–90%. The imperative need for alternative treatment methods for terminal-stage patients is crucial, particularly in underdeveloped countries facing limited resources. Surveillance programs have been implemented in developed nations to identify high-risk HCC patients. However, resource constraints in underdeveloped regions often result in later-stage HCC presentations, precluding curative treatments [2]. Various imaging modalities are available for liver tumor evaluation, with Ultrasonography (US) emerging as a cost-effective screening method, surpassing computed tomography (CT) and magnetic resonance imaging (MRI) in terms of cost, absence of radiation exposure, and avoidance of contrast agent nephrotoxicity. US demonstrates 60% sensitivity and over 95% specificity for screening chronic liver disease (liver cirrhosis) and virus-infected patients [3]. When a liver nodule suggests HCC, further diagnostic investigation is necessary. Biopsy is recommended for confirmed HCC cases with nodules exceeding 2 cm and low serum alpha-fetoprotein (AFP), or when resection, ablation, or liver transplantation is not feasible. Importantly, biopsy is discouraged in cases of elevated AFP and suggestive imaging, with treatment following established guidelines [4]. The molecular and histopathological pathways of HCC initiation remain incompletely understood. Indications point to genetic changes in pre-neoplastic hepatic cells and the gradual accumulation of mutations as culprits in malignant transformation leading to HCC [5]. HCC can manifest as a single liver nodule or multiple nodules, categorized by pathologists into well, moderate, and poorly differentiated stages. Well-differentiated HCC closely resembles healthy hepatic cells, while poorly differentiated HCC exhibits distinct structures and characteristics compared to normal cells.

1.1 Liver lobule: The organization of hepatic parenchyma

The liver lobule, defined as the microscopic functional unit of hepatic parenchyma, comprises a central terminal hepatic venule surrounded by up to six terminal portal triads, forming a polygonal unit. Hepatocytes, arranged in a single-cell-thick layer between the central venule and terminal portal triad branches, produce bile. Blood flows from sinusoids on each side of hepatocytes to the central venule. Along the sinusoidal lining, diverse cells include hepatic stellate cells, lymphoid cells, and Kupffer cells—specialized macrophages with roles in phagocytosis and inflammatory response initiation. Liver stellate cells, rich in retinoid, contribute to liver fibrosis and cirrhosis in response to injuries [6].

Toxic substance exposure and immune responses in the liver induce inflammation through Kupffer and stellate cells, potentially leading to necrosis. Persistent inflammation may progress to liver fibrosis and cirrhosis, characterized by distorted anatomy, septa, nodule formation, and altered blood flow within liver lobules. Cirrhosis emerges as a prominent risk factor for HCC, with continuous liver cell necrosis and regeneration increasing exposure to mutagenic agents. This dynamic process results in genetic and epigenetic changes, transforming normal hepatic cells into dysplastic foci, liver nodules, and ultimately HCC [7].

1.2 Staging systems

In CT scans, HCC typically manifests as a focal nodule with early arterial phase enhancement and rapid contrast washout during the portal vein phase in a three-phase contrast study. Conversely, on MRI scans, HCC presents as a lesion with high signal intensity.

The prognosis of HCC hinges on both underlying liver disease and tumor characteristics, prompting the proposal of multiple staging systems. The TNM classification of malignant tumors (TNM) system, devised by the American Joint Committee of Cancer (AJCC), emphasizes tumor, lymph nodes, and metastasis. While TNM staging predicts disease prognosis post-tumor resection, it falls short in evaluating liver function. Notably, tumor characteristics remain predictive of the ultimate outcome [8].

The Barcelona clinic liver cancer (BCLC) staging system currently governs HCC management, aligning treatment options with patient outcomes. Stage 0 patients, with tumors smaller than 2 cm, normal portal pressure, and normal serum bilirubin, offer a favorable scenario for tumor resection, yielding long-term survival rates exceeding 75%. Patients with larger tumors, a single tumor smaller than 5 cm, or multiple tumors (none exceeding 3 cm) are candidates for liver transplantation or surgical excision based on cirrhosis status [9].

Contemporary HCC treatments, such as liver resection and orthotopic liver transplantation, serve as gold standard procedures. Diverse hepatectomy techniques, aided by ablation methods and transcatheter devices, contribute to hepatic surgery. Liver transplantation proves effective for HCC patients with tumors up to 5 cm or three lesions, each 3 cm or smaller, achieving a 5-year overall survival rate of 75% [5]. Due to the prevalent late-stage presentation of HCC, systemic and palliative therapies dominate treatment approaches. Notably, HCC displays resistance to chemotherapy, leading to a surge in the popularity of targeted therapies as a novel strategy against the disease [10].

1.3 Expression of growth factors

The vascularity of HCC is marked by structural and functional irregularities crucial for tumor development. Vascular secretion is imperative for HCC cell proliferation, with pro-angiogenic growth factors and their receptor tyrosine kinases (RTK) playing a significant role in angiogenesis within the tumor microenvironment [11]. Prominent growth factors such as vascular endothelial growth factor (VEGF), epidermal growth factor (EGF), fibroblast growth factor (FGF), insulin-like growth factor (IGF), and platelet-derived growth factor (PDGF) contribute to heightened vascularity and cancer cell proliferation, expressing not only in cancer cells but also in the surrounding healthy tissue. Their expression correlates with disease progression and vascular invasion [12].

RTKs are transmembrane proteins facilitating extracellular signal transduction that play a pivotal role in HCC development. Activated upon growth factor binding, RTKs initiate various intracellular signaling pathways, including PI3K/AKT/mTOR and RAS/RAF/MEK/ERK, fostering angiogenesis, cell survival, and the migration, proliferation, and differentiation of endothelial cells [13]. Dysregulation of RTKs, whether through genomic rearrangements, gain-of-function mutations, overexpression, or constant stimulation from overexpressed growth factors, results in sustained kinase activity [13, 14].

Rat sarcoma (RAS) and rapidly accelerated fibrosarcoma (RAF) participate in intracellular signaling cascades that activate gene expression [15]. RAS activation of RAF leads to mitogen-activated protein kinase kinase (MEK) activation, subsequently activating extracellular signal-regulated kinase (ERK) and regulating various intracellular substrates and gene expression associated with cell proliferation [16]. ERK activation is linked to cancer cell proliferation.

The expression of growth factors like EGF in tumors is linked to tumor invasion, while PDGF expression is implicated in metastasis. Endothelial cell proliferation significantly contributes to tumor infiltration into healthy parenchyma and vascular invasion [17].

The phosphatidylinositol-3 kinase (PI3K) pathway, pivotal for cancer cell proliferation and survival, is implicated in HCC. Activating AKT and subsequently phosphorylating mTOR, the PI3K pathway influences cell proliferation and survival. Suppression of apoptosis through BCL2 associated agonist of cell death (BAD) inactivation is also attributed to this pathway. Notably, phosphatase and tensin homolog (PTEN), a regulator of the PI3K pathway, undergoes downregulation in HCC cells, and its suppression is linked to tumor grade progression, tumor stage, and poor overall prognosis [18].

Tyrosine kinase-type receptors, including VEGF receptors (VEGFR), PDGF receptors (PDGFR), EGF receptors (EGFR), FGF receptors (FGFR), and IGF receptors (IGFR), play a crucial role in HCC development. Activation of these receptors initiates the intracellular RAS in the RAF/MEK/ERK pathway. AP-1 proteins such as c-JUN and c-FOS activate the expression of genes associated with cell proliferation and heightened vascularity [19]. The RAF/MEK/ERK pathway activation is implicated in HCC progression, particularly in HBV-related cases [20].

Among the investigated signaling pathways, the VEGF and VEGFR-mediated pathway is one of the most extensively studied. VEGF-A isoforms, particularly VEGF165, are overexpressed in various tumors and are associated with disease progression, invasion, metastasis, and poorer patient survival. Consequently, anti-angiogenic agents focusing on VEGF-A and VEGFR-2 are under development [21].

No dominant pathway has been identified, leading to the evaluation of drugs targeting individual pathways for HCC treatment. Due to HCC’s high resistance to systematic chemotherapy, current efforts concentrate on identifying signal pathways and genes associated with carcinogenesis and chemotherapy resistance [22].

2. Results

2.1 Multi-targeted tyrosine kinase inhibitors: First-line treatment

2.1.1 Sorafenib

The pioneer in targeted therapy for advanced HCC is Sorafenib, approved by the American Food and Drug Administration (FDA). This oral molecular agent exerts simultaneous effects on multiple targets, inhibiting Raf-1 within the RAF/MEK/ERK pathway and RTK involved in angiogenesis and tumor progression [23].

The Sorafenib Hepatocellular Carcinoma Assessment Randomized Protocol (SHARP) trial, a pivotal phase III study, led to FDA approval. Involving 602 patients with advanced HCC, the trial demonstrated a marked advance in median overall survival (OS). More specifically, it went from 7.9 to 10.7 months (hazard ratio (HR) = 0.69, p = 0.001). Time to progression (TTP) radiologically also prolonged from 2.8 to 5.5 months (HR = 0.58, p < 0.001). While the overall response rate (ORR) was 2%, the Sorafenib group exhibited a significantly higher disease control rate (DCR) compared to the placebo group (43% vs. 32%, p = 0.002) [24].

Additional trials in Asia further validated the efficacy of Sorafenib, revealing increased OS (6.5 vs. 4.2 months, HR = 0.68, p = 0.014) and prolonged TTP (2.8 vs. 1.4 months, HR = 0.57, p = 0.0005). The partial response was 3.3%, and the DCR was notably higher in the Sorafenib group (53% vs. 12%, p = 0.0019) [25].

Subsequent analyses of SHARP trial data considered baseline patient characteristics, affirming that Sorafenib improved OS and DCR independently of these factors [26]. These findings solidified Sorafenib as the standard therapy for advanced HCC.

Sorafenib has also been investigated in combination therapies. In a phase II trial, Sorafenib followed by concurrent modified FOLFOX (folinic acid, fluorouracil, oxaliplatin) (mFOLFOX) exhibited promising efficacy against advanced HCC, albeit with moderate toxicity [27, 28, 29]. Another study explored the combination of Sorafenib with transarterial chemoembolization (TACE), demonstrating a favorable safety profile and high DCR [30]. Comparative studies, such as Sorafenib + TACE vs. TACE alone, consistently revealed superior outcomes with combination therapy [31].

However, a phase III trial assessing Sorafenib post-TACE failed to demonstrate a significant prolongation of TTP. No marked difference in OS was observed between the Sorafenib and placebo groups [32]. While Sorafenib shows promise in combination therapies, further studies are warranted to establish the optimal approach.

2.1.2 Lenvatinib

Lenvatinib, an oral multi-kinase inhibitor (MKI), hinders tumor cell proliferation and angiogenesis by targeting VEGFR1–3, FGFR1–4, PDGFR alpha, RET protein, and c-Kit protein. Following promising results in a phase II trial [33], the phase III REFLECT trial compared Lenvatinib to Sorafenib as a first-line treatment in 954 patients with advanced HCC. Lenvatinib demonstrated non-inferiority, with a median OS of 13.6 vs. 12.3 months for Sorafenib (HR = 0.92, 95% CI: 0.79–1.06), and a superior TTP of 8.9 vs. 3.7 months (HR = 0.63, 95% CI: 0.53–0.73, p < 0.0001). Lenvatinib also exhibited a higher response rate (24.1% vs. 9.2%, p < 0.001) [34].

Reanalysis of the REFLECT study suggested potential underestimation of Lenvatinib’s favorable effect, primarily due to imbalances in AFP concentrations and additional treatments between the two groups [35].

2.1.3 Sunitinib

Sunitinib is a tyrosine kinase inhibitor (TKI), with anti-angiogenic and antitumor behaviors, that targets VEGFR-1–3, PDGFR (alpha and beta), c-KIT, FLT3, and RET. Initial phase II studies indicated antitumor activity but with notable toxicities [36, 37, 38]. Subsequent phase III trials comparing Sunitinib to Sorafenib as a first-line treatment demonstrated inferior OS with Sunitinib (7.9 vs. 10.2 months, HR = 1.30, p = 0.0014), leading to the premature closure of the study due to safety concerns [39].

Combination therapies, such as Sunitinib plus TACE, showed improved OS and TTP compared to TACE alone in certain studies [40, 41]. However, conflicting results emerged, indicating the need for further investigation to establish the efficacy and safety of such combinations [42].

2.1.4 Linifanib

Linifanib, an oral TKI targeting VEGFR and PDGFR, was compared to Sorafenib in a randomized phase III trial for first-line treatment. While Linifanib exhibited favorable outcomes in terms of TTP and ORR, it did not translate into improved OS compared to Sorafenib. Linifanib was also associated with a higher incidence of adverse events, leading to dose reductions/interruptions and discontinuations, suggesting lower tolerability than Sorafenib [43].

2.1.5 Erlotinib

Erlotinib is an orally administered inhibitor of EGFR tyrosine kinase [44]. EGFR has been identified as a factor contributing to the endurance of HCC cells against sorafenib. Inhibiting EGFR has shown augmented effectiveness of sorafenib, as demonstrated by Ezzoukhry et al., who utilized model cell lines (Huh7, Hep3B, HepG2) to assess the response of HCC cells to therapeutic agents. They observed a cooperative outcome of EGFR inhibitors and sorafenib on the activity of the RAF-MEK-ERK kinase cascade in HCC cells which are EGFR-positive [45].

The phase III SEARCH trial, a randomized, placebo-controlled, double-blind study, compared erlotinib and sorafenib with sorafenib as a monotherapy in patients with untreated, advanced HCC. With 720 participants meeting inclusion criteria, including unresectable HCC, Child-Pugh liver function class A, life expectancy greater than 12 weeks, and an Eastern Cooperative Oncology Group Performance Status (ECOG-PS) of 0 or 1, the trial did not detect a significant difference in the median OS between the two groups (9.5 vs. 8.5 months, HR = 0.929, p = 0.408). Additionally, no significant difference in TTP (3.2 vs. 4.0 months, HR = 1.135, p = 0.18) was observed. Thus, the addition of erlotinib to sorafenib did not improve survival in advanced HCC patients based on this data analysis [46].

Erlotinib has also been investigated in combination treatments. In a phase II trial evaluating the efficacy of gemcitabine, oxaliplatin, and erlotinib (G + O + E) in 26 HCC patients, a DCR of 42% at 24 weeks was achieved. The median progression-free survival (PFS) was 35 weeks, and the median OS was 26 weeks. The observed difference between PFS and OS was mainly attributed to cirrhosis-related deaths without disease progression [47].

2.1.6 Foretinib

Foretinib is an oral MKI targeting mesenchymal epithelial transition (MET), reactive oxygen species (ROS), recepteur d’origine nantais (RON), anexelekto (AXL), tunica interna endothelial cell kinase 2 (TIE-2), and VEGFR2. In a single-arm, phase I/II study conducted in Asia, foretinib’s safety and efficacy were evaluated as a first-line treatment for advanced HCC in patients with Child-Pugh A liver disease. With a maximum tolerated dose of 30 mg/day showing no major toxicity, among 35 patients assessed for efficacy, foretinib exhibited a median TTP of 4.24 months (95% CI: 2.79–9.59). The DCR was 82.9% (95% CI: 66.4–93.4), and the median OS was 15.7 months [48].

Although foretinib shows efficiency against advanced HCC, the conclusive evidence is still pending, necessitating randomized phase III trials to confirm its efficacy.

2.1.7 Donafenib

Donafenib is a novel, oral, small-molecule MKI, a modified form of sorafenib with a trideuterated N-methyl group. Following promising results from phase I studies, a randomized, phase II/III trial was conducted in a China. The trial included 659 patients with advanced HCC and Child-Pugh A, who had not previously undergone systematic treatment. Among them, 328 were treated with donafenib, and 331 with sorafenib, with 594 having HBV-related HCC. Donafenib demonstrated a higher ORR and DCRs of 4.6% and 30.8%, respectively, compared to sorafenib (2.7% ORR and 28.7% DCR). Although the median PFS for donafenib vs. sorafenib was not significantly different (3.7 vs. 3.6 months, HR = 0.909; 95% CI: 0.763–1.082; p = 0.0570), a significant difference was observed in OS. Between donafenib and sorafenib the OS was 12.1 vs. 10.3 months (HR = 0.831; 95% CI: 0.699–0.988; p = 0.0245). Donafenib also demonstrated a more favorable safety profile, with significantly fewer drug-related grade ≥ 3 adverse events (AEs) and lower rates of dose interruptions and reductions than sorafenib [49].

Hence, donafenib could be considered as part of the first-line treatment for advanced HCC, particularly in selected populations.

2.2 Multi-targeted tyrosine kinase inhibitors: Second-line treatment

2.2.1 Regorafenib

Regorafenib is an oral MKI targeting VEGFR 1–3, TIE 2, PDGFR beta, FGFR, RET, KIT, RAF-1, and B-Raf. Initially approved for refractory colorectal cancer and gastrointestinal stromal tumors, regorafenib’s efficacy and safety in HCC were evaluated in a phase II study, showing anticancer activity and acceptable tolerability. Subsequently, the RESORCE trial, a phase III, double-blinded, placebo-controlled study, assessed regorafenib in patients with disease progression after first-line sorafenib treatment. With 573 participants meeting inclusion criteria, regorafenib demonstrated improved median OS (10.6 vs. 7.8 months, HR = 0.63, p < 0.0001) and median PFS (3.1 vs. 1.5 months, HR = 0.46, p < 0.0001), along with significantly higher ORR (11% vs. 4%) [50].

The primary objective of this study was achieved successfully, suggesting that the sequential use of two MKIs with partly overlapping targets provides a survival benefit in HCC, especially for patients progressing after sorafenib treatment.

2.2.2 Cabozantinib

Cabozantinib is an oral TKI suppressing MET, VEGFR-2, and RET. A phase II randomized discontinuation trial (RDT) involving 41 HCC patients with Child-Pugh A liver function who had received 1 systemic agent or less, demonstrated a median OS of 11.5 months and a median PFS of 5.2 months [44]. Subsequently, the CALESTIAL trial assessed cabozantinib’s efficacy in individuals with advanced HCC, specifically those with Child-Pugh A status and an ECOG-PS of 0 or 1, who had undergone one to two prior systematic treatments, including sorafenib. A total of 707 patients were randomly assigned to receive either 60 mg of cabozantinib once daily or a placebo. Following the second interim analysis, the trial achieved its primary goal, demonstrating a statistically significant and clinically relevant enhancement in median OS compared to the placebo group (10.2 vs. 8.0 months, HR = 0.76, 95% CI: 0.63–0.92, p = 0.0049). Secondary endpoints, including median PFS (5.2 vs. 1.9 months, HR = 0.44, p < 0.001) and ORR (4% vs. 0.4%, p = 0.0086), were also significantly improved [51]. In a post hoc analysis, patients who had previously received only sorafenib were included, revealing improved OS and PFS with cabozantinib regardless of the duration of prior sorafenib treatment [52].

Cabozantinib stands as a viable option for second- or third-line treatment in patients with advanced HCC.

2.2.3 Tivantinib

Tivantinib is a selective inhibitor of c-MET, a tyrosine kinase receptor encoded by the protooncogene c-MET. Upon attachment to hepatocyte growth factor (HGF), the MET signaling pathway is activated, influencing various cellular processes such as differentiation, angiogenesis, cell invasion, and metastasis. Dysregulated MET expression is implicated in several human cancers, including HCC, and is associated with a poorer prognosis [53].

Following phase I and Ib trials, a randomized phase II trial compared tivantinib to placebo as a second-line treatment in 71 patients. The analysis revealed a longer TTP in patients treated with tivantinib compared to placebo (1.6 vs. 1.4 months, HR = 0.64, 90% CI: 0.43–0.94, p = 0.04). Notably, in patients with high c-MET expression determined by immunohistochemistry, tivantinib demonstrated a more significant improvement in median TTP compared to placebo (2.7 vs. 1.4 months, HR = 0.43, 95% CI: 0.19–0.97, p = 0.03). Moreover, the median OS was better with tivantinib (7.2 vs. 3.8 months, HR = 0.38, 95% CI: 0.18–0.81, p = 0.01). However, the tivantinib group experienced higher and more severe cases of neutropenia and anemia, with four deaths attributed to neutropenia [54, 55].

Subsequently, a phase III study with 340 patients failed to demonstrate the effectiveness of tivantinib in unresectable HCC with radiographically confirmed progression after sorafenib-containing systemic therapy. No significant differences were observed in OS, PFS, TTP, or DCR between the tivantinib and placebo groups [56]. Another phase III study with 195 patients also did not show statistically significant results [57]. Thus, tivantinib has not been proven as an effective second-line agent, but the potential efficacy of concomitant inhibition of c-MET and VEGF warrants further investigation [56].

2.2.4 Axitinib

Axitinib is a highly effective inhibitor targeting VEGFR 1, 2, and 3 with specificity. In a phase II trial conducted without control group involvement, patients diagnosed with advanced HCC, ranging from Child-Pugh A to B7 status, and experiencing disease progression post-treatment with tyrosine kinase inhibitors (TKI)/antiangiogenic drugs were enrolled, the median OS for all patients was 7.1 months, and PFS was 3.6 months. The tumor control rate at 16 weeks was 42.3%, with one partial response and 10 stable disease cases. Adverse events led to treatment discontinuation in 26.7% of patients [58]. However, a randomized phase II study comparing axitinib to placebo in second-line treatment of advanced HCC did not demonstrate its superiority in terms of OS. The median OS was 12.7 months with axitinib/BSC and 9.7 months with placebo/BSC, but the difference was not statistically significant. Notably, excluding patients intolerant to prior antiangiogenic treatment showed a greater difference in OS, and PFS and TTP were significantly longer in the axitinib arm [59].

Axitinib’s potential as a first-line treatment in combination with TACE also showed promising results in a phase II trial, with a 2-year survival rate of 43.7% and a median OS of 18.8 months [60]. In conclusion, axitinib exhibits significant antitumor activity in HCC, but further study through phase III clinical trials is crucial.

2.2.5 Anlotinib

Anlotinib is an orally administered TKI targeting VEGFR, FGFR, PDGFR, and c-kit. In a phase II clinical trial, two cohorts were studied for first-line and second-line treatments. Cohort 1, including 26 patients without prior TKI treatment, showed a 12-week PFS rate of 80.8% and a 24-week PFS rate of 54.2%. The median TTP was 5.9 months, and the median OS was 12.8 months. In cohort 2, including 24 patients with previous treatment, the 12-week PFS rate was 72.5%, with a 24-week PFS rate of 46.6%. The median TTP and OS were 4.6 months and 18.0 months, respectively. Anlotinib’s safety profile was favorable, and patients with lower baseline plasma levels of CXCL1 showed longer TTP in both cohorts [61].

Anlotinib’s efficacy was also explored in combination with penpulimab (Anti-PD-1) as a first-line therapy [62]. Overall, anlotinib demonstrates satisfactory efficacy in both first-line and second-line treatments for advanced HCC, emphasizing the need for further studies to confirm these findings and explore combination therapies.

2.2.6 Tepotinib

Tepotinib is an orally available, potent, and highly selective MET inhibitor. In a phase Ib study and subsequent phase II trial, tepotinib demonstrated positive outcomes in advanced HCC patients who had received at least 4 weeks of sorafenib treatment. The median TTP was 2.1 months, PFS was 1.5 months, and OS was 7.2 months. The DCR was 57.1%, with stable disease, complete response, and partial response observed. No major safety issues were reported, and patients with MET over-expression exhibited more favorable efficacy profiles [63].

In another phase Ib/II study with Asian patients, tepotinib improved TTP compared to sorafenib without significant toxicity. The median Independent Review Committee (IRC)-assessed TTP favored tepotinib, and the investigator-assessed TTP showed similar results. While there was no difference in OS, tepotinib demonstrated a higher DCR [64]. Tepotinib appears to be an efficient agent for both first- and second-line treatment in advanced HCC, particularly in patients with MET over-expression. Confirmatory evidence from phase III trials is necessary to validate these findings.

2.3 Anti-VEGF therapies

2.3.1 Ramucirumab

Ramucirumab is an injectable agent, a human IgG1 monoclonal antibody that selectively targets the extracellular domain of VEGFR2. By doing so, it obstructs ligand binding and hinders the stimulation of the receptor-mediated pathway in endothelial cells.

In a phase II trial, ramucirumab’s potential as a first-line monotherapy for anticancer activity was investigated [65]. Subsequently, in the phase III REACH trial, its efficacy was evaluated as a second-line treatment in 565 patients with advanced HCC who had either failed treatment with sorafenib or were intolerant to it. Although no significant superiority in overall survival (OS) was observed (9.2 vs. 7.6 months, HR = 0.87, p = 0.14), secondary endpoints such as progression-free survival (PFS) (2.8 vs. 2.1 months, HR = 0.63, p < 0.001) and objective response (7% vs. <1%) favored the ramucirumab treatment arm. Further subgroup analysis was conducted, which identified efficacy in patients with an elevated baseline AFP level, particularly those with AFP ≥400 ng/mL (median OS 7.8 vs. 4.2 months, HR = 0.67, p = 0.006) [66].

Building on this observation, the REACH-2 study, a randomized phase III trial, focused on evaluating ramucirumab vs. placebo as second-line treatments in patients with AFP greater than 400 ng/mL. Enrolling 292 patients with BCLC stage B or C disease, refractory or not amenable to locoregional therapy, and Child-Pugh class A liver disease, the study demonstrated a statistically significant improvement in OS with ramucirumab (8.5 months; 95% CI: 7.0–10.6) compared to placebo (7.3 months [5.4–9.1]) with an HR = 0.710 (95% CI: 0.531–0.949), p = 0.0199. Additionally, PFS and DCR were significantly superior in the ramucirumab group [67].

Ramucirumab was also investigated in combination with emibetuzumab, showing potential anticancer activity in a phase Ib/II study across various solid tumors [19]. In summary, ramucirumab exhibits satisfactory efficacy in advanced HCC as a second-line treatment, particularly in a selected population with high AFP levels, and may hold promise in combination therapy.

2.3.2 Bevacizumab

Bevacizumab is a humanized monoclonal antibody that targets VEGF-A. Explored extensively for treating advanced HCC, several phase II trials have examined its safety and efficacy either as a monotherapy or in combination with other agents.

In a phase II trial with 46 patients, bevacizumab showed a median PFS of 6.9 months and a 1-year OS rate of 53%, reaching 28% and 23% at 2 and 3 years, respectively [68]. Another phase II trial with 38 patients reported a DCR of 42% at 16 weeks, a median PFS of 3 months, and a median OS of 8 months [69]. Notably, these studies enrolled patients with Child-Pugh A or compensated B, and observed adverse events were mainly hypertension and gastrointestinal bleeding.

Combination therapies involving bevacizumab, such as with gemcitabine and oxaliplatin or capecitabine and oxaliplatin, demonstrated potential anticancer activity in phase II studies [70]. Further exploration included combining bevacizumab with erlotinib, yielding promising results in some phase II studies, although others failed to show efficacy [71].

A randomized phase II study comparing bevacizumab plus erlotinib with sorafenib alone demonstrated comparable efficacy but better safety and tolerability for the combination [72].

Bevacizumab was also studied in combination with TACE. Although some trials showed potential efficacy, others revealed mixed results and safety concerns [73, 74, 75].

The pivotal shift in the treatment landscape occurred with a global, open-label, phase III trial comparing bevacizumab plus atezolizumab against sorafenib as a first-line treatment [76]. Atezolizumab, a programmed death 1 (PD-1) inhibitor, combined with bevacizumab, outperformed sorafenib, becoming the new standard of care. The trial demonstrated superior OS, PFS, and DCR with manageable safety issues [77]. Consequently, the combination of bevacizumab and atezolizumab is now considered the preferred first-line treatment for advanced HCC.

2.3.3 Apatinib

Apatinib stands out as a highly selective and potent TKI that effectively hampers angiogenesis by specifically targeting VEGFR2.

In a phase III trial, which was randomized, double-blind, placebo-controlled, and multicenter, the efficacy of apatinib as a second-line treatment for advanced HCC was evaluated. Among the 393 participants eligible for further analysis, 261 were assigned to the apatinib group, while 132 received a placebo. All participants had a Child-Pugh score of 7 or lower, with 41% having previously received sorafenib treatment. Approximately one-fifth of the participants had undergone more than one systematic therapy before receiving apatinib. The findings indicated a median overall survival (OS) of 8.7 months (95% CI: 7.5–9.8) in the apatinib group compared to 6.8 months (95% CI: 5.7–9.1) in the placebo group. The median progression-free survival (PFS) was 4.5 months (95% CI: 3.9–4.7) in the apatinib group and 1.9 months (95% CI: 1.9–2.0) in the placebo group, with a hazard ratio of 0.471 (95% CI: 0.369–0.601, p < 0.0001). The apatinib arm also exhibited higher rates of objective response and disease control. Adjusting for poststudy treatment further emphasized the efficacy of apatinib. Interestingly, the favorable effect appeared more pronounced in patients aged 65 years or younger, those with AFP ≥200 μg/L, those without previous sorafenib treatment, and those with only one previous systemic therapy. Notably, 12-month PFS and 12-month OS estimates showed overlapping 95% confidence intervals (CIs) between the apatinib and placebo groups. Treatment-related adverse events (AEs) were manageable, with hypertension being the most common grade 3 or 4 AE (28% of patients) [78].

Following encouraging results from a phase I study [79], a non-randomized, open-label, phase II trial explored apatinib’s efficacy in combination with camrelizumab, a high-affinity, humanized IgG4-κ PD-1 monoclonal antibody. Enrolling 190 patients with advanced HCC and Child-Pugh A, the combination exhibited a promising ORR of 34.3% (first-line) and 22.5% (second-line). The 12-month survival rates were 74.7% and 68.2%, respectively. Median PFS for both cohorts demonstrated effectiveness at 5.7 months (first-line) and 5.5 months (second-line). Disease control rates were favorable, and safety profiles, though resulting in treatment discontinuation for 12.1% of patients, indicated a promising outcome [80]. A randomized, open-label, international, multicenter, phase III clinical study comparing this combination with sorafenib as a first-line treatment is currently underway (NCT03764293).

Furthermore, apatinib showcased positive outcomes in combination with TACE. In a single-center randomized controlled trial involving 44 patients with moderate and advanced HCCs and Child-Pugh A or B, the group receiving TACE plus apatinib demonstrated significantly prolonged Median PFS compared to the TACE-only group (12.5 vs. 6.0 months, p < 0.05). However, the reduction in AFP after 3 months and differences in ORR at 3, 6, 9, and 12 months were not statistically significant between the two groups [81].

In summary, apatinib has proven effective as a second-line treatment and shows promise in revolutionizing HCC treatment as part of combination therapies.

2.4 TGF-β receptor inhibitor

The TGF-β signaling pathway emerges as a therapeutic target for HCC. Galunisertib (LY2157299 monohydrate), an oral small-molecule inhibitor of TGF-β receptor I kinase, took center stage in a phase II trial evaluating its efficacy as a second-line treatment.

In this trial, 149 patients with advanced HCC and Child-Pugh class A or B7 were registered. Among them, 109 had AFP ≥1.5 × upper limit of normal (ULN) (Part A), and 40 had AFP <1.5 × ULN (Part B). The study revealed favorable results, with a median TTP of 2.7 months (95% CI: 1.5–2.9) in Part A and 4.2 months (95% CI: 1.7–5.5) in Part B. Median OS was 7.3 months (95% CI: 4.9–10.5) in Part A and 16.8 months (95% CI: 10.5–24.4) in Part B. The OS for Part A (150 mg twice daily) vs. Part B (150 mg twice daily) was significantly longer (HR = 2.1, 95% CI: 1.3–3.3). Responders to AFP demonstrated significantly longer TTP (4.3 vs. 1.5 months). The safety profile was notably favorable [82].

Exploring further, a phase II study assessed the combination of galunisertib and sorafenib as a first-line treatment in 47 patients. The study revealed a TTP of 4.1 months (95% CI: 2.8, 6.5) and OS of 18.8 months (95% CI: 14.8, 24.8). Prognostic value was observed for AFP and TGF-β1. Responders to TGF-β1 (decrease of >20% from baseline) exhibited longer OS (22.8 vs. 12.0 months, p = 0.038) [83].

In summary, therapeutic options for advanced HCC are provided by the TGF-β pathway, with galunisertib being extensively studied and showing favorable efficacy. However, further phase III trials are warranted to solidify these findings.

2.5 Immunotherapy

The immune system plays a crucial role in the body’s defense against cancer, and immunotherapy has emerged as a promising strategy for cancer treatment. In the context of HCC, T-cells, a type of immune cell, are pivotal in recognizing and attacking tumor cells. T-cell activation is a complex process involving interactions with tumor-specific antigens and co-stimulatory signals. One key co-stimulatory signal involves the engagement of CD28 on T-cells with B7 molecules on antigen-presenting cells (APCs) [84]. However, this activation also triggers inhibitory pathways, such as the role of cytotoxic T-lymphocyte protein-4 (CTLA-4) and programmed cell death-1 (PD-1). CTLA-4, akin to CD28, binds to B7 molecules but suppresses T-cell responses. Similarly, PD-1, expressed by activated T-cells, B cells, and myeloid cells, interacts with its ligands PD-L1 and PD-L2 on APCs, leading to the downregulation of T-cell responses. Monoclonal antibodies (mAbs) targeting these immune checkpoints aim to enhance the anti-tumor immune response by inhibiting these inhibitory pathways, representing a novel and promising approach in cancer treatment [85].

2.5.1 Nivolumab

Nivolumab, a fully human immunoglobulin G4 monoclonal antibody targeting PD-1, has shown promise in treating advanced HCC. The CheckMate 040 trial assessed its safety and efficacy in patients with advanced HCC, including those with chronic viral hepatitis. The results demonstrated a response rate (RR) of 20%, DCR of 64%, and a median OS of 15 months. Notably, the manageable toxicity profile and positive responses led to FDA approval [86].

The combination of nivolumab and ipilimumab (anti-CTLA-4) was also evaluated in the same trial. Arm A, with nivolumab 1 mg/kg plus ipilimumab 3 mg/kg, showed an ORR of 32% and a median OS of 22.8 months, leading to FDA approval for second-line treatment of advanced HCC [87].

In the phase III trial (CheckMate 459), nivolumab was compared with sorafenib as a first-line treatment for advanced HCC. Nivolumab demonstrated a higher ORR (15%), a complete response rate of 4%, and a lower incidence of severe adverse events compared to sorafenib [88].

2.5.2 Pembrolizumab

Pembrolizumab, another anti-PD-1 monoclonal antibody, has shown efficacy in advanced HCC. In a phase II trial, pembrolizumab demonstrated an ORR of 17% and a DCR of 62% in patients previously treated with sorafenib [89]. A subsequent phase III trial (KEYNOTE-240) reinforced these findings, leading to FDA approval as a second-line treatment [90].

2.5.3 Avelumab

Avelumab, a fully human anti-PD-L1 monoclonal antibody, exhibited efficacy in advanced HCC in a phase II study. With a 10% ORR and a 73.3% DCR, avelumab demonstrated a median PFS of 3.5 months and a median OS of 14.2 months, making it a potential therapeutic option. Further research is needed to establish its role definitively [91].

2.5.4 Tremelimumab plus durvalumab

The combination of tremelimumab (anti-CTLA-4) and durvalumab (anti-PD-L1) has shown promise in a phase I/II study for second-line treatment of advanced HCC. The T300 + D arm exhibited the highest ORR (24%) and median OS (18.73 months). While effective, optimal dosage and potential monotherapy use require further investigation [92].

2.5.5 Sintilimab

Sintilimab, a selective anti-PD-1 antibody, in combination with IBI305 (bevacizumab biosimilar), demonstrated superiority over sorafenib in a phase II/III study (ORIENT-32) for first-line treatment of HBV-related advanced HCC. With a significant improvement in ORR, DCR, and OS, this combination presents a promising alternative for this specific patient population [93].

2.6 CAR-T cell therapy

Chimeric antigen receptor T-cell (CAR-T) therapy, established for hematological malignancies, is being investigated for its efficacy and safety in HCC. In a phase II trial targeting CD133, CAR-T cells demonstrated a manageable safety profile and encouraging clinical outcomes in patients with advanced HCC. Further studies are crucial to integrate CAR-T cell therapy into advanced HCC treatment strategies [94].

3. Discussion

Despite notable advancements and the wider array of therapeutic options available, the overall prognosis for HCC remains modest. The introduction of sorafenib marked a significant milestone, enhancing our comprehension of the disease and contributing to prolonged survival among patients. As the inaugural systematically approved TKI, sorafenib set the stage for progressing toward a curative approach. Subsequently, considerable headway has been achieved in this direction.

Although initial outcomes of various treatments fell short in comparison to sorafenib, the groundbreaking results from the IMBRAVE150 trial have revolutionized first-line advanced HCC treatment. This combination has now become the established standard of care, significantly improving OS for HCC patients [77]. The landscape of immunotherapy appears promising, offering reliable monotherapies or combination treatments in both first and second-line settings [77, 88, 90, 93]. Simultaneously, antiangiogenic therapies, including bevacizumab, ramucirumab, and apatinib, demonstrate substantial efficacy as second-line treatments [67, 78]. Combination therapies involving anti-PD-1 and anti-angiogenesis antibodies exhibit a more favorable anti-HCC efficacy by inhibiting tumor angiogenesis and curbing immunosuppressive cell activity in the tumor microenvironment. This fosters the re-expression of cytotoxic T cells, reinstating their antitumor effect [95]. The ongoing surge in clinical trials on antineoplastic agents, as evident from the 750-plus registered trials (https://clinicaltrials.gov [Accessed: November 13, 2022]), underscores the scientific community’s keen interest in exploring novel therapeutic avenues.

Neoadjuvant therapy, exemplified by the promising results of dovitinib, an anti-angiogenesis factor, presents another potential avenue that warrants further exploration [96]. Concurrent application of TACE and systemic treatments demonstrates favorable outcomes [40, 41, 42, 75, 81].

In the realm of immunotherapy, there is much to unravel. While immunotherapy has showcased significant benefits in melanoma, its application in other cancers like pancreatic cancer and cholangiocarcinoma is noteworthy [97]. CAR-T therapy, particularly targeting Glypican-3 (GPC3) and anti-CD133, shows promise in HCC, backed by both in vitro and in vivo success and numerous ongoing clinical studies [97].

Exploring alternative pathways of carcinogenesis, such as the TGF-β-associated pathway, introduces additional treatment options [23]. Molecular enhancements to existing drugs, as seen with donafenib, a deuterated sorafenib derivative with improved safety, further diversify therapeutic choices [49]. Clinical studies investigating donafenib in combination with anti-PD1 agents are underway (NCT04612712, NCT04503902).

Addressing the challenge of second-line treatment post-intolerance or failure of the initial therapy is critical. While numerous agents show promise, especially in patients treated with alternatives like bevacizumab/atezolizumab or lenvatinib, the data on second-line agents necessitate thorough collection.

The evolving landscape of targeted therapies prompts a reevaluation of chemotherapy agents’ efficacy in advanced HCC. Combinatorial treatments involving chemotherapy and targeted agents hold promise, although larger patient cohorts in phase III clinical trials are indispensable for conclusive results [27, 28].

Exploration of specific molecular targets, including long non-coding RNAs (lncRNAs) and micro-RNAs (miRNAs), remains largely pre-clinical. While several miRNAs and lncRNAs emerge as potential therapeutic targets, their clinical studies are limited, posing safety concerns [98]. The extensive use of mRNA vaccines during the COVID pandemic may expedite this research.

In the era of diverse therapeutic options, personalized treatment selection remains challenging. Ramucirumab’s efficacy in patients with AFP ≥400 ng/mL is an established knowledge [66, 67]. Biomarkers like c-met expression for tivantinib and TGF-β1 for TGF-β receptor inhibitors could predict treatment responses [59, 60, 83]. Identification of five biomarkers related to OS and TTP after regorafenib treatment emphasizes the need for further studies to establish such connections [99].

The etiology of HCC plays a role in therapeutic response variability. Sorafenib may offer greater benefits in HCV-positive patients than in HBV-positive patients. Notably, donafenib, a modified sorafenib derivative, improves OS in HBV-related HCC, presenting a viable alternative [49]. Conversely, immunotherapy might not be as beneficial for NASH-related HCC, necessitating exploration of alternative strategies [100].

Most clinical trials involve patients with preserved hepatic function (Child-Pugh A or B7), leaving limited data for other patients. Cautionary use of sorafenib in patients with impaired hepatic function is suggested, while comprehensive studies on the safety of other treatment options in similar populations are imperative. Understanding the pathogenesis of HCC is crucial for improving OS, emphasizing the necessity for deeper insights into molecular complexities. The evolving era will likely rely on combination treatments, necessitating continued research into genomic alterations and the development of HCC stem cell lines for novel drug testing.

4. Conclusions

In summary, HCC stands as the predominant primary liver malignancy and a prevalent cancer type. Resistant to chemotherapy, HCC patients in terminal stages find orthotopic liver transplantation as the optimal treatment. Targeted therapies have emerged as a focal point in HCC treatment, with various drugs targeting different molecular pathways showing promise. Sorafenib, initially groundbreaking, was surpassed by the atezolizumab and bevacizumab combination. Many other drugs have demonstrated efficacy or are currently under evaluation. This comprehensive review not only outlines the mechanisms of action of these agents but also discusses their advantages and drawbacks. Notably, it compares the features of newly developed agents with established treatment regimes. Understanding the current knowledge on HCC management is crucial for guiding future studies, shedding light on potential perspectives, and facilitating the development of advanced drugs.