Hepatitis B reactivation in patients receiving targeted therapies

ABSTRACT

Objectives: Hepatitis B virus (HBV) reactivation may occur spontaneously, during or after antiviral therapy, or when receiving immunosuppressive chemotherapy. HBV reactivation has also been reported in cancer patients receiving targeted therapies, such as monoclonal antibody and mammalian target of rapamycin (mTOR) inhibitor. This review article is aimed to discuss the issue regarding chronic HBV reactivation in patients receiving targeted therapies, with a special focus on tyrosine kinase inhibitors.

Methods: Using MEDLINE search, the literature relevant to hepatitis B reactivation, monoclonal antibody therapy and tyrosine kinase inhibitor was reviewed.

Results: HBV-infected patients receiving tyrosine kinase inhibitors (TKIs) may develop HBV reactivation even with resolved HBV infection status. Although the exact mechanism of TKI-induced HBV reactivation remains unclear, off-target immunological effects of TKI may play an important role in contributing to HBV reactivation.

Discussion: Further well-designed studies are necessary to find out the incidence and mechanism of HBV reactivation in patients receiving TKIs. Screening, monitoring and prophylaxis or pre-emptive antiviral therapy is mandatory in HBV patients who are going to receive immunosuppressive therapy or targeted therapy.

Conclusion: HBV reactivation may occur in patients receiving monoclonal antibodies and TKIs, even with resolved HBV infection status. Although the exact mechanism of TKI-induced HBV reactivation remains unclear, off-target immunological effects of TKI may play an important role in contributing to HBV reactivation.

KEYWORDS:

• Hepatitis B reactivation
• targeted therapy
• monoclonal antibody
• tyrosine kinase inhibitor
• off-target
• immunological effects

1. Introduction

Hepatitis B virus (HBV) infection is a global public health issue, with about 350 million people being chronically infected [1,2]. Nearly 780 000 deaths every year are attributed to HBV-related complications [3], and about 50% of the mortality secondary to hepatocellular carcinoma (HCC) was associated with HBV [4]. Chronic HBV infection is a state of dynamic interactions among HBV, hepatocytes, and host immune cells. HBV reactivation, which is defined as an abrupt alanine aminotransferase (ALT) elevation > 5 times normal upper limit (NUL), may occur spontaneously [5], during or after antiviral therapy, or in the setting of immunosuppression and/or chemotherapy [6]. Furthermore, HBV reactivation has been reported in cancer patients receiving targeted therapies, such as monoclonal antibody [7,8], and mammalian target of rapamycin (mTOR) inhibitor [9,10]. This review article is aimed to discuss the issue regarding chronic HBV reactivation in patients receiving targeted therapies, with a special focus on tyrosine kinase inhibitors (TKIs).

2. HBV reactivation in patients receiving monoclonal antibody therapy

In recent years, the use of monoclonal antibody therapy has improved the effective management of various hematological malignancy and immune-mediated diseases. However, these biologic agents may induce a profound immunosuppression that may trigger HBV reactivation.

2.1. Rituximab (anti-CD20)

Rituximab is being currently used for the treatment of CD20-positive B-cell lymphoma and chronic lymphocytic leukemia (CLL). Addition of rituximab in the chemotherapy regimen further increased risk and severity of HBV reactivation in hepatitis B surface antigen (HBsAg)-negative and hepatitis B core antibody (HBcAb)-positive lymphoma patients [11]. In a recent prospective study of 150 HBsAg-negative and HBcAb-positive lymphoma patients who received rituximab-CHOP (cyclophosphamide, doxorubicin, vincristine, prednisolone)-based chemotherapy, the incidence of HBV reactivation was 10.4 per 100 person-year [12]. Furthermore, a recent meta-analysis confirmed a measurable and potentially substantial risk of HBV reactivation in HBsAg-negative/HBcAb-positive patients exposed to rituximab [13].

Additionally, rituximab is also effective in the treatment of other conditions, such as idiopathic thrombocytopenic purpura, chronic rheumatoid arthritis and ABO-incompatible or positive crossmatch kidney transplantation [14–16]. In a recent retrospective study of 44 HBsAg-negative/HBcAb-positive patients who received rituximab treatment for rheumatoid arthritis, the incidence of HBV reactivation was 9.1%, with a mean treatment duration of 25.4 months from first rituximab treatment to the onset of HBV reactivation [17]. Furthermore, in a study of 172 HBsAg-negative/HBcAb-positive HBV patients who underwent living donor kidney transplant, 5 of 49 (10.2%) patients in the rituximab treatment group experienced HBV reactivation, with one patient died of hepatic failure [16]. Although the control of HBV infection is mainly mediated by HBV-specific cytotoxic T lymphocytes (CTLs), B lymphocytes are still essential for antigen presentation. Therefore, depletion of circulating B cells after rituximab treatment might result in dysregulation in host immunity, thus leading to HBV reactivation [18].

2.2. Alemtuzumab (anti-CD52)

Alemtuzumab is a humanized chimeric lymphocytotoxic monoclonal antibody that recognizes the antigen CD52, which is expressed on all CLL cells and indolent lymphomas. Alemtuzumab is Food and Drug Administration (FDA) approved for use in CLL patients who have received alkylating agents and failed to respond to fludarabine therapy. Alemtuzumab treatment may cause cell death by complement activation, antibody-dependent cellular cytotoxicity and apoptosis, resulting in a profound and prolonged T and B lymphocyte depletion [19]. Although the risk of HBV reactivation after anti-CD52 immunosuppression is not well defined, there have been reports on the development of HBV reactivation after alemtuzumab therapy. Alemtuzumab-containing chemotherapy regimens are associated with high risk of severe HBV-related hepatitis and occult HBV reactivation (detectable HBV DNA in the liver with negative HBsAg status) [19,20].

2.3. Mogamulizumab

Mogamulizumab is a humanized monoclonal antibody targeting the C-C chemokine receptor 4 (CCR4) that has been approved in Japan for the treatment of relapse/refractory adult T-cell leukemia/lymphoma (ATL). ATL is a rare subtype of lymphoma with a higher prevalence in Japan and certain regions in Middle East and South America. There are only a few case reports of HBV reactivation in patients treated with mogamulizumab [21–23]. In the study of Totani et al. [23], HBV reactivation was observed in 3 of 24 (12.5%) ATL patients with resolved HBV infection (Anti-HBc-positive, anti-HBs-positive and undetectable HBV DNA level). Mogamulizumab was administered before HBV reactivation in two of three HBV-reactivated patients. CCR4 is a chemokine receptor expressed on T-helper type 2 (Th2) cells and regulatory T cells and is thought to have an important role in the balance of immune system. A reduction of numbers of CCR4-expression cells after mogamulizumab treatment might be associated with the imbalance of antiviral immunity, thus resulting in the development of HBV reactivation in these cases [22,23].

2.4. Anti-TNF-α

Biologic therapies targeting the tumor necrosis factor-alpha (TNF-α) have emerged as a new class of drugs that are increasingly used for rheumatic, digestive and dermatological diseases. Four TNF-α antagonists are antibodies against TNF-α: infliximab, a chimeric mouse/human monoclonal antibody; adalimumab and golimumab, humanized monoclonal antibodies and certolizumab, a pegylated Fab fragment of humanized monoclonal antibody. Various reported cases have shown that TNF-α inhibition facilitates HBV reactivation and replication, with fulminant liver failure or fatal outcomes [24]. TNF-α blockade in patients with chronic HBV infection may be beneficial because long-term inhibition of TNF-α could protect the hepatocytes from progressive fibrosis; however, in another aspect, failure to secrete adequate amounts of TNF-α may cause impairment of circulating CTL responses [24,25]. Among different anti-TNF-α agents, infliximab seems to be more frequently associated with HBV reactivation, although the reasons are still unclear [25]. In a systemic analysis of 257 patients receiving TNF-α antagonists (89 HBsAg-positive, and 168 HBcAb-positive), HBV reactivation occurred in 35 (39%) of 89 HBsAg-positive patients. Hepatitis flare with ALT > 5× NUL occurred in 12 (34%) of the 35 patients with HBV reactivation. Furthermore, the rate of HBV reactivation in 168 HBcAb-positive patients was 5%, with one patient died due to fulminant liver failure [26].

3. HBV reactivation in patients receiving TKIs

A TKI is a pharmaceutical drug that inhibits tyrosine kinases. Numerous TKIs aiming at various tyrosine kinases have been generated and proven to be effective anti-tumor agents and anti-leukemic agents. There have been several studies regarding HBV reactivation after TKI treatments; however, the exact mechanism of TKI-induced HBV reactivation remains unclear due to limited case reports. Reported cases of HBV reactivation in patients receiving TKIs are summarized in Table 1.

Table 1. Reported cases of HBV reactivation in patients receiving TKIs.

TKI	Target	PreTx HBsAg	PreTx HBeAg	Tx	Outcome [reference]
Imatinib	Bcr/Abl	+	−	LAM	Died [27]
		+	−	LAM	Died [28]
		+	−	Conservative	Resolved [29]
		+	−	LAM; LDLT	Resolved [30]
		+	−	LDLT	Resolved [31]
		+	−	ETV	Resolved [32]
		+	+	ETV	Resolved [33]
Nilotinib	Bcr/Abl	+	−	ETV	Resolved [33]
Dasatinib	Src/Abl	−	−	LAM; ETV	Resolved [37]
Erlotinib	EGFR	+	−	ETV	Resolved [38]
Ibrutinib	Bruton’s tyrosine kinase	−	−	ETV	Resolved [39]

ETV, entecavir; LAM, lamivudine; LDLT, living donor liver transplantation; PreTx, pretreatment; Tx, treatment.

3.1. Imatinib mesylate

Imatinib mesylate (IM) (Glivec; Novartis, Basel, Switzerland) is a selective Bcr/Abl TKI and is now widely used in the treatment of chronic myeloid leukemia (CML) and gastrointestinal stromal tumors. Several studies have shown that HBV reactivation can be induced by the treatment of IM [27–33]. The mechanism of IM-induced HBV reactivation remains unclear due to limited case reports. In vitro studies have shown that IM can inhibit antigen-specific T-cell activation and proliferation [34,35]. In the study of Lai et al. [33], HBV-related hepatitis flares were observed after complete molecular or cytogenetic responses after IM treatment. Furthermore, in the study of Mohty et al. [36], CML patients with complete molecular or cytogenetic response after IM treatment restored function of plasmacytoid dendritic cells, which are crucial effectors in innate immunity. Evidences from these two studies suggested that immune modulation after IM treatment may play a role in contributing to HBV reactivation.

3.2. Nilotinib

Nilotinib (Tasigna; Novartis, Basel, Switzerland), a second-generation Bcr/Abl TKI, was approved for CML patients with resistance or intolerance to IM. Although HBV reactivation induced by IM has been reported [27–33], there is only one reported case in the current literature regarding nilotinib-related HBV reactivation [33]. In the study of Lai et al., the hepatitis flare in the patient receiving nilotinib treatment was 5 months before achieving complete cytogenetic response [33]. The authors proposed that nilotinib treatment might provoke a different pathway other than that of IM treatment to achieve immune restoration, thus leading to hepatitis flare in this patient.

3.3. Dasatinib

Dasatinib (Sprycel, Bristol-Myers Squibb, USA) is a Src/Abl TKI currently approved for the treatment of Philadelphia chromosome (Bcr/Abl)-positive CML and acute lymphoblastic leukemia. In the study of Ando et al. [37], the authors reported a case of CML patient who received dasatinib treatment and was HBsAg-negative before treatment. The patient achieved a complete cytogenetic response at sixth month and a major molecular response at eighth month of dasatinib therapy. Three years after dasatinib therapy, the patient experienced increased level of HBV DNA and became HBsAg-positive. The patient maintained a major molecular response to CML at the time of HBV reactivation. The authors proposed that dasatinib-related immunosuppression, emergence of HBV mutants and age-related immunosuppression may be responsible for the HBV reactivation in this case.

3.4. Erlotinib

Erlotinib (Tarceva, Genentech, OSI Pharmaceuticals, USA) is an epidermal growth factor receptor (EGFR)-targeted TKI, which is considered to be a standard of care for EGFR-mutated non-small-cell lung cancer. In a recent case report, a 62-year-old woman received whole brain radiation and concurrent erlotinib 150 mg per day because of the diagnosis of EGFR-mutated stage IV adenocarcinoma of the lung [38]. Erlotinib was discontinued 1 month later due to large-volume diarrhea. The patient developed hepatitis flare with an ALT level of 267 IU/L 8 days after erlotinib withdrawal. Hepatitis serologies showed positive for HBsAg, and the HBV DNA level was 307 IU /ml at the time of hepatitis flare. However, there are drawbacks of this study. First, the HBV DNA level at the time of hepatitis flare was 307 IU/ml, which was relatively low for patients with HBV reactivation. Second, there was no pretreatment level of HBV DNA and the patient’s liver panel trended down without intervention. Therefore, erlotinib-related hepatotoxicity cannot be excluded as the cause of hepatitis flare in this study.

3.5. Ibrutinib

Ibrutinib (Imbruvica, Janssen, Pharmacyclics, USA), a selective and covalent inhibitor of Bruton’s tyrosine kinase, has been approved for the treatment of patients with mantle cell lymphoma, CLL, and Waldenström’s macroglobulinemia. In a recent case report by de Jésus Ngoma et al., an 80-year-old man received ibrutinib treatment for the diagnosis of CLL [39]. Before treatment, the patient was HBsAg-negative and with a low HBV DNA level of 429 IU/ml. However, after 5 months of ibrutinib treatment, HBV reactivation developed in this patient with an elevated HBV DNA level of 23 076 000 IU/ml and HBsAg became positive. Ibrutinib has been shown to irreversibly inhibit activation of Th2 cells after T-cell receptor stimulation and further cause compensatory activation of Th1 cells and CTL [40]. This dynamic change of immune response after ibrutinib treatment can provide a clue to HBV reactivation in this case.

4. Off-target immunological effects of TKI and HBV reactivation

The therapeutic effects of targeted agents have been assumed to exert their actions only on malignant cells through their debulking capability. For example, IM selectively kills Philadelphia-chromosome-positive (Ph+) myeloid lineage cells in the bone marrow and periphery, but exerts no effects on Ph+ hematopoietic stem cells. However, results from the French STIM trial showed that 41% of CML patients could stop IM treatment without relapse after achieving a complete molecular response lasting for 2 years [41]. The findings of STIM trial were further supported by recent clinical trials [42–45], meaning that the activity of IM might be prolonged beyond cessation of treatment by inducing or reinstating immunosurveillance. As for the off-target immunological effects on patients with chronic HBV infection, it is worth noting that CML patients receiving IM [27,33] or dasatinib treatment [37] developed HBV reactivation after achieving complete molecular or cytogenetic responses. Results of these studies imply that CML patients achieving complete molecular responses might be at risk of HBV reactivation even after cessation of treatment.

To date, very few in vivo human studies have addressed the long-term impact of TKIs on the immune function. In vitro studies have shown that IM can inhibit antigen-specific T-cell activation and proliferation [34,35]. In vitro data for second-generation TKIs showed that there was impaired antigen-specific T-cell response for nilotinib [46,47] and dasatinib [48–51]. In the study of Powers et al., the immunological effects of 64 CML patients under TKIs treatment were investigated [52]. The study showed that there were reduced levels of regulatory T cells, with expansion of T lymphocytes clones in patients receiving IM, nilotinib, or dasatinib. Furthermore, 3% (5 of 16) of IM-treated, 14% (2 of 14) of nilotinib-treated, and 31% (5 of 16) of dasatinib-treated patients had clonal expansions of large granular lymphocytes (LGLs). LGLs, which comprised natural killer cells and CTL, are essential for innate and acquired immunity against viral infection and neoplasm [53]. Ibrutinib is a selective and covalent inhibitor of Bruton's tyrosine kinase, an important kinase in B-cell receptor signaling and survival. However, ibrutinib has been shown to irreversibly inhibit activation of Th2 cells after T-cell receptor stimulation and further cause compensatory activation of Th1 cells and CTL [40]. On the other hand, although the control of HBV infection is mainly mediated by HBV-specific CTLs, B lymphocytes are still essential for antigen presentation. A recent study has shown that B-cell response to pneumococcal vaccine is significantly impaired in chronic phase CML patients receiving IM, nilotinib, or dasatinib [54]. Furthermore, in vitro coincubation of B cells with plasma from chronic phase CML patients receiving IM, nilotinib, or dasatinib induced dose-dependent inhibition of Bruton's tyrosine kinase and its downstream substrate. Results from this study demonstrated that TKIs may interfere with B-cell activation and induction of humoral immune response in vivo through their off-target multikinase inhibitory effects.

Taken together, the findings of these studies imply that the off-target immunological effect of various TKIs might modulate cellular immune response. Therefore, we propose that the off-target immunological effects of TKIs might have an important role in contributing to HBV reactivation in patients receiving TKIs.

5. Treatment recommendations for HBV reactivation

5.1. Screening

Early identification of HBV infection in patients receiving immunosuppression therapy is the key to prevent HBV reactivation. Several clinical predictors for HBV reactivation have been identified and can be categorized into host factors, viral factors and treatment-related factors (Table 2). The host factors for HBV reactivation were male, young age, ALT elevation before immunosuppression and type of malignancy [55,56]. The viral factors for HBV reactivation were high HBV viral load, positive HBsAg, positive HBeAg, precore mutant, core promoter mutant and low anti-HBs titer [7,55,57]. The treatment-related factors included intensity and duration of immunosuppression, rituximab-based regimen, high-dose steroid and hematopoietic stem cell transplantation [7,55,58]. Combination of these risk factors can be used to stratify patients into high, intermediate and low risk for HBV reactivation. Recommendations from major societies for HBV screening before immunosuppression therapy are summarized in Table 3. Guidelines from major societies suggest that candidates for immunosuppressive chemotherapy should be screened for HBsAg and anti-HBc prior to initiation of treatment. HBsAg-positive patients should be tested for HBV DNA levels before starting antiviral therapy. Furthermore, both APASL and EASL guidelines recommend that HBsAg-negative patients with positive anti-HBc antibodies should be tested for HBV DNA. HBsAg-negative, anti-HBc-positive patients with detectable serum HBV DNA should be treated similarly to HBsAg-positive patients.

Table 2. Risk factors for HBV reactivation.

	Risk factors
Host factors	Male Young age ALT elevation before immunosuppression Type of malignancy
Viral factors	High HBV viral load Positive HBsAg Positive HBeAg Precore mutant Core promoter mutant Low anti-HBs titer
Treatment-related factors	Intensity and duration of immunosuppression Rituximab-based regimen High-dose steroid Hematopoietic stem cell transplantation

Table 3. Recommendations of HBV screening tests for patients before receiving immunosuppressive chemotherapy.

Major societies	Recommended screening tests before immunosuppressive chemotherapy
	HBsAg	Anti-HBc	Anti-HBs
ASCO	High risk	High risk	No
APASL	Yes	Yes	No
EASL	Yes	Yes	No
AASLD	High risk	High risk	No
CDC	Yes	Yes	Yes

AASLD: American Association for the Study of Liver Disease; APASL: Asian Pacific Association for the Study of the Liver; ASCO: American Society of Clinical Oncology; CDC: Center for Disease Control; EASL: European Association for the Study of the Liver.

Currently, there is no screening recommendation for patients receiving TKIs. We endorse pretreatment screening tests of HBsAg and anti-HBc because of reported cases of HBV reactivation in patients with pretreatment HBsAg-negative status (Table 1). HBsAg-positive patients and HBsAg-negative patients with positive anti-HBc antibodies should be tested for HBV DNA level before starting TKIs.

5.2. Antiviral therapy

Regarding antiviral treatment in HBsAg-positive patients receiving immunosuppressive chemotherapy, recommendations from three major societies suggest prophylactic treatment (Table 4). AASLD guideline suggests that antiviral therapy should last for 6 months after completion of chemotherapy [59]. Both APASL and EASL guidelines suggest that prophylactic antiviral therapy should last for 12 months after cessation of chemotherapy [60,61]. As for choice of oral antiviral therapy, all three major societies suggest that lamivudine can be used if treatment duration is short; however, entecavir or tenofovir can be used if treatment duration is longer.

Table 4. Recommendations of oral antiviral therapy according to guidelines of three major societies.

	Management guidelines of chronic HBV
	AASLD 2009	APASL 2015	EASL 2012
Time to start	Prophylactic treatment	Prophylactic treatment	Pre-emptive treatment
Time to stop	Baseline HBV DNA < 2000 IU/ml: 6 months after completion of chemotherapy Baseline HBV DNA ≥ 2000 IU/ml: continue treatment till endpoints	12 months after completion of chemotherapy	12 months after completion of chemotherapy
Antiviral agent	Short duration ≤ 12 months: LAM or LdT Longer duration: ETV or TDF	LAM; ETV or TDF if longer duration	Short duration and HBV DNA < 2000 IU/ml: LAM Lengthy chemotherapy and high HBV DNA: ETV or TDF

AASLD: American Association for the Study of Liver Disease; APASL: Asian Pacific Association for the Study of the Liver; EASL: European Association for the Study of the Liver; ETV: Entecavir; LAM: Lamivudine; LdT: Telbivudine; TDF: Tenofovir.

Currently, there is no treatment recommendation for HBV reactivation in patients receiving TKIs. For HBsAg-positive patients or HBsAg-negative/anti-HBc-positive patients with high HBV DNA level before receiving TKIs, we endorse prophylactic treatment with entecavir or tenofovir. As for HBsAg-negative/anti-HBc-positive patients with undetectable HBV DNA prior to TKIs, we propose regular testing of HBsAg and HBV DNA levels every 3 months. Once HBsAg become positive and/or HBV DNA level is elevated, antiviral therapy should be considered. However, further prospective studies may be needed to establish management strategies of HBV reactivation in patients receiving TKIs.

6. Conclusions

In summary, hepatitis flares in patients with chronic HBV infection are the results of CTL-mediated immune responses against HBV. HBV reactivation is an important issue in HBV-infected patients receiving immunosuppressive chemotherapy and biologic therapy, such as monoclonal antibodies and TKIs. HBV-infected patients receiving TKIs may develop HBV reactivation even with resolved HBV infection status. Although the exact mechanism of TKI-induced HBV reactivation remains unclear, off-target immunological effects of TKI may play an important role in contributing to HBV reactivation. Further well-designed studies are necessary to find out the incidence and mechanism of HBV reactivation in patients receiving TKIs. Finally, screening, monitoring and prophylaxis or pre-emptive antiviral therapy is mandatory in HBV patients who are going to receive immunosuppressive therapy or targeted therapy.

Disclosure statement

No potential conflict of interest was reported by the authors.