A phase 2 dose-finding study of lonafarnib and ritonavir with or without interferon alpha for chronic delta hepatitis.

BACKGROUND AND AIMS: Proof-of-concept studies demonstrated lonafarnib (LNF), a first-in-class oral prenylation inhibitor, efficacy in patients infected with HDV. The lonafarnib with ritonavir for HDV-2 (LOWR-2) study's aim was to identify optimal combination regimens of LNF + ritonavir (RTV) ± pegylated interferon alpha (PEG-IFNα) with efficacy and tolerability for longer-term dosing. Here we report the safety and efficacy at end of treatment for up to 24 weeks. APPROACH AND RESULTS: Fifty-five patients with chronic HDV were consecutively enrolled in an open-label, single-center, phase 2 dose-finding study. There were three main treatment groups: high-dose LNF (LNF ≥ 75 mg by mouth [po] twice daily [bid] + RTV) (n = 19, 12 weeks); all-oral low-dose LNF (LNF 25 or 50 mg po bid + RTV) (n = 24, 24 weeks), and combination low-dose LNF with PEG-IFNα (LNF 25 or 50 mg po bid + RTV + PEG-IFNα) (n = 12, 24 weeks). The primary endpoint, ≥2 log10 decline or < lower limit of quantification of HDV-RNA from baseline at end of treatment, was reached in 46% (6 of 13) and 89% (8 of 9) of patients receiving the all-oral regimen of LNF 50 mg bid + RTV, and combination regimens of LNF (25 or 50 mg bid) + RTV + PEG-IFNα, respectively. In addition, multiple patients experienced well-tolerated transient posttreatment alanine aminotransferase increases, resulting in HDV-RNA negativity and alanine aminotransferase normalization. The proportions of grade 2 and 3 gastrointestinal adverse events in the high-dose versus low-dose groups were 49% (37 of 76) and only 22% (18 of 81), respectively. CONCLUSIONS: LNF, boosted with low-dose RTV, is a promising all-oral therapy, and maximal efficacy is achieved with PEG-IFNα addition. The identified optimal regimens support a phase 3 study of LNF for the treatment of HDV.

A Phase 2 Randomized Placebo-Controlled Adjuvant Trial of GI-4000, a Recombinant Yeast Expressing Mutated RAS Proteins in Patients with Resected Pancreas Cancer.

Purpose: GI-4000, a series of recombinant yeast expressing four different mutated RAS proteins, was evaluated in subjects with resected ras-mutated pancreas cancer. Methods: Subjects (n = 176) received GI-4000 or placebo plus gemcitabine. Subjects' tumors were genotyped to identify which matched GI-4000 product to administer. Immune responses were measured by interferon-γ (IFNγ) ELISpot assay and by regulatory T cell (Treg) frequencies on treatment. Pretreatment plasma was retrospectively analyzed by matrix-assisted laser desorption/ionization-time-of-flight (MALDI-ToF) mass spectrometry for proteomic signatures predictive of GI-4000 responsiveness. Results: GI-4000 was well tolerated, with comparable safety findings between treatment groups. The GI-4000 group showed a similar pattern of median recurrence-free and overall survival (OS) compared with placebo. For the prospectively defined and stratified R1 resection subgroup, there was a trend in 1 year OS (72% vs. 56%), an improvement in OS (523.5 vs. 443.5 days [hazard ratio (HR) = 1.06 [confidence interval (CI): 0.53-2.13], p = 0.872), and increased frequency of immune responders (40% vs. 8%; p = 0.062) for GI-4000 versus placebo and a 159-day improvement in OS for R1 GI-4000 immune responders versus placebo (p = 0.810). For R0 resection subjects, no increases in IFNγ responses in GI-4000-treated subjects were observed. A higher frequency of R0/R1 subjects with a reduction in Tregs (CD4+/CD45RA+/Foxp3low) was observed in GI-4000-treated subjects versus placebo (p = 0.033). A proteomic signature was identified that predicted response to GI-4000/gemcitabine regardless of resection status. Conclusion: These results justify continued investigation of GI-4000 in studies stratified for likely responders or in combination with immune check-point inhibitors or other immunomodulators, which may provide optimal reactivation of antitumor immunity. ClinicalTrials.gov Number: NCT00300950.

Pharmacokinetics, safety, and tolerability of the 2- and 3-direct-acting antiviral combination of AL-335, odalasvir, and simeprevir in healthy subjects.

This Phase I, open-label, two-group, fixed-sequence study evaluated the pharmacokinetics and safety of AL-335, odalasvir, and simeprevir in healthy subjects. Group 1 (n = 16) received AL-335 800 mg once daily (QD) (days 1-3, 11-13, and 21-23), simeprevir 150 mg QD (days 4-23), and odalasvir 150 mg (day 14) followed by 50 mg QD (days 15-23). Group 2 (n = 16) received the same AL-335 regimen as in Group 1 plus odalasvir 150 mg (day 4) followed by 50 mg QD (days 5-23) and simeprevir 150 mg QD (days 14-23). Blood samples were collected to determine plasma concentrations of AL-335 (prodrug) and its metabolites, ALS-022399 (monophosphate precursor) and ALS-022227 (parent nucleoside), odalasvir, and simeprevir. Thirty-two subjects were enrolled. Odalasvir and simeprevir given alone, or in combination, increased AL-335 area under plasma concentration-time curve over 24 hours (AUC 0-24 h) 3-, 4-, and 7- to 8-fold, respectively; ALS-022399 AUC 0-24 h increased 2-, 2-, and 3-fold, respectively. Simeprevir had no effect on ALS-022227 AUC 0-24 h, whereas odalasvir with/without simeprevir increased ALS-022227 AUC 0-24 h 1.5-fold. AL-335 had no effect on odalasvir or simeprevir pharmacokinetics. Odalasvir and simeprevir AUC 0-24 h increased 1.5- to 2-fold for both drugs when coadministered irrespective of AL-335 coadministration. Study medications were well tolerated with no serious adverse events. One subject prematurely discontinued study drugs (unrelated event). This study defined the preliminary pharmacokinetic and safety profiles of the combination of AL-335, odalasvir, and simeprevir in healthy subjects. These data support the further evaluation of this combination for the treatment of chronic hepatitis C virus infection.

Whole Recombinant Saccharomyces cerevisiae Yeast Expressing Ras Mutations as Treatment for Patients With Solid Tumors Bearing Ras Mutations: Results From a Phase 1 Trial.

We are developing whole, heat-killed, recombinant Saccharomyces cerevisiae yeast, engineered to encode target proteins, which stimulate immune responses against malignant cells expressing those targets. This phase 1 trial, enrolling patients with advanced colorectal or pancreas cancer, was designed to evaluate safety, immunogenicity, response, and overall survival of ascending doses of the GI-4000 series of products, which express 3 different forms of mutated Ras proteins. The study enrolled 33 heavily pretreated subjects (14 with pancreas and 19 with colorectal cancer), whose tumors were genotyped before enrollment to identify the specific ras mutation and thereby to identify which GI-4000 product to administer. No dose limiting toxicities were observed and no subject discontinued treatment due to a GI-4000 related adverse event (AE). The majority of AEs and all fatal events were due to underlying disease progression and AE frequencies were not significantly different among dose groups. GI-4000 was immunogenic, as Ras mutation-specific immune responses were detected on treatment in ∼60% of subjects. No objective tumor responses were observed but based on imaging, clinical status and/or biochemical markers, stable disease was observed in 6 subjects (18%) on day 29, while 1 subject had stable disease at days 57 and 85 follow-up visits. The median overall survival was 3.3 months (95% confidence interval, 2.3-5.3 mo), and 5 subjects survived past the 48-week follow-up period. No significant dose-dependent trends for survival were observed. This first clinical trial in humans with GI-4000 demonstrated a favorable safety profile and immunogenicity in the majority of subjects.

Safety, tolerability and immunogenicity of GS-4774, a hepatitis B virus-specific therapeutic vaccine, in healthy subjects: a randomized study.

BACKGROUND: GS-4774 is a recombinant, heat-killed, yeast-based immunotherapy engineered to express hepatitis B virus (HBV)-specific antigens. GS-4774 is being developed as a therapeutic vaccine for chronic HBV infection. The aim of this study was to assess the safety, tolerability and immunogenicity of GS-4774 in healthy subjects. DESIGN: This was a randomized, open-label, dose-ascending study. Subjects were allocated to one of three dose groups (n=20 per group) to receive 10, 40 or 80 yeast units (YU; 1YU=10(7) yeast) of GS-4774 in two immunization regimens (five subcutaneous injections at weekly intervals with one monthly booster or three subcutaneous injections at monthly intervals). T-cell-mediated responses were determined by interferon (IFN)-γ enzyme-linked immunospot (ELISpot) assay and lymphocyte-proliferation assay (LPA). RESULTS: Adverse events were reported by 39 of 60 (65%) subjects; all were mild or moderate and none was serious. Adverse events occurred most frequently in the highest dose group, 80YU, and the number of individual events was higher after weekly immunization than monthly. The most common adverse events were injection-site reactions. Most (88%) subjects responded to GS-4774 by at least one of the T-cell assays. Following immunization with GS-4774, IFN-γ-producing T-cells specific for HBV antigens were detectable in 30 (51%) subjects. The ELISpot response was observed at all doses, with the highest frequency of responders occurring at the highest dose (10YU: 45%; 40YU: 35%; 80YU: 74%). Proliferative responses to HBV recombinant antigens were observed in 90% subjects; responses were mainly independent of GS-4774 dose and immunization regimen. CONCLUSIONS: GS-4774 was safe and well-tolerated in healthy subjects with injection-site reactions being the most frequently reported adverse events. With both weekly and monthly regimens, GS-4774 provided HBV-specific immune responses at all doses evaluated. Further evaluation of GS-4774 is ongoing in patients with chronic HBV infection. CLINICAL TRIAL REGISTRY: Clinicaltrials.gov (NCT01779505).

Phase II study of the GI-4000 KRAS vaccine after curative therapy in patients with stage I-III lung adenocarcinoma harboring a KRAS G12C, G12D, or G12V mutation.

INTRODUCTION: Patients with early-stage lung cancer have a high risk of recurrence despite multimodality therapy. KRAS-mutant lung adenocarcinomas are the largest genetically defined subgroup, representing 25% of patients. GI-4000 is a heat-killed recombinant Saccharomyces cerevisiae yeast-derived vaccine expressing mutant KRAS proteins. The present phase II study assessed the feasibility, immunogenicity, and safety of the GI-4000 vaccine in patients with early-stage, KRAS-mutant lung cancer. MATERIALS AND METHODS: Patients with stage I-III KRAS-mutant lung cancer who completed curative therapy were enrolled. The patients received the genotype matched GI-4000 vaccine for ≤ 3 years or until intolerance, disease recurrence, or death. The KRAS antigen T-cell response was assessed using the interferon-gamma enzyme-linked immunospot assay in peripheral blood mononuclear cells. The study was powered to detect an immune response in ≥ 25% of patients. RESULTS: A total of 24 patients were enrolled over 28 months. No vaccine-related serious adverse events occurred. One patient withdrew consent because of pain at the injection site. The study met its primary endpoint, with 50% of patients developing an immune response to mutant KRAS. The median number of vaccinations received was 15 (range, 1-19). Ten patients experienced disease recurrence, and 6 died. Compared with the genotypically matched historical controls, the recurrence rates were equivalent but overall survival showed a favorable trend. CONCLUSION: GI-4000 was well tolerated and immunogenic when used as consolidation therapy in patients with stage I-III KRAS-mutant lung cancer. The patterns of recurrence and death observed in the present study can be used to design a randomized study of GI-4000 with overall survival as the primary endpoint.

A whole recombinant yeast-based therapeutic vaccine elicits HBV X, S and Core specific T cells in mice and activates human T cells recognizing epitopes linked to viral clearance.

Chronic hepatitis B infection (CHB) is characterized by sub-optimal T cell responses to viral antigens. A therapeutic vaccine capable of restoring these immune responses could potentially improve HBsAg seroconversion rates in the setting of direct acting antiviral therapies. A yeast-based immunotherapy (Tarmogen) platform was used to make a vaccine candidate expressing hepatitis B virus (HBV) X, surface (S), and Core antigens (X-S-Core). Murine and human immunogenicity models were used to evaluate the type and magnitude of HBV-Ag specific T cell responses elicited by the vaccine. C57BL/6J, BALB/c, and HLA-A*0201 transgenic mice immunized with yeast expressing X-S-Core showed T cell responses to X, S and Core when evaluated by lymphocyte proliferation assay, ELISpot, intracellular cytokine staining (ICS), or tumor challenge assays. Both CD4+ and CD8+ T cell responses were observed. Human T cells transduced with HBc18-27 and HBs183-91 specific T cell receptors (TCRs) produced interferon gamma (IFNγ following incubation with X-S-Core-pulsed dendritic cells (DCs). Furthermore, stimulation of peripheral blood mononuclear cells (PBMCs) isolated from CHB patients or from HBV vaccine recipients with autologous DCs pulsed with X-S-Core or a related product (S-Core) resulted in pronounced expansions of HBV Ag-specific T cells possessing a cytolytic phenotype. These data indicate that X-S-Core-expressing yeast elicit functional adaptive immune responses and supports the ongoing evaluation of this therapeutic vaccine in patients with CHB to enhance the induction of HBV-specific T cell responses.

Phase I trial of a recombinant yeast-CEA vaccine (GI-6207) in adults with metastatic CEA-expressing carcinoma.

Yeast-CEA (GI-6207) is a therapeutic cancer vaccine genetically modified to express recombinant carcinoembryonic antigen (CEA) protein, using heat-killed yeast (Saccharomyces cerevisiae) as a vector. In preclinical studies, yeast-CEA induced a strong immune response to CEA and antitumor responses. Patients received subcutaneous vaccines every 2 weeks for 3 months and then monthly. Patients were enrolled at 3 sequential dose levels: 4, 16, and 40 yeast units (10(7) yeast particles/unit). Eligible patients were required to have serum CEA > 5 ng/mL or > 20 % CEA(+) tumor block, ECOG PS 0-2, and no history of autoimmunity. Restaging scans were performed at 3 months and then bimonthly. Peripheral blood was collected for the analysis of immune response (e.g., by ELISPOT assay). Twenty-five patients with metastatic CEA-expressing carcinomas were enrolled. Median patient age was 52 (range 39-81). A total of 135 vaccines were administered. The vaccine was well tolerated, and the most common adverse event was grade 1/2 injection-site reaction. Five patients had stable disease beyond 3 months (range 3.5-18 months), and each had CEA stabilization while on-study. Some patients showed evidence post-vaccination of increases in antigen-specific CD8(+) T cells and CD4(+) T lymphocytes and decreases in regulatory T cells. Of note, a patient with medullary thyroid cancer had substantial T cell responses and a vigorous inflammatory reaction at sites of metastatic disease. Yeast-CEA vaccination had minimal toxicity and induced some antigen-specific T cell responses and CEA stabilization in a heterogeneous, heavily pre-treated patient population. Further studies are required to determine the clinical benefit of yeast-CEA vaccination.

Immunological targeting of tumor cells undergoing an epithelial-mesenchymal transition via a recombinant brachyury-yeast vaccine.

The embryonic T-box transcription factor brachyury is aberrantly expressed in a range of human tumors. Previous studies have demonstrated that brachyury is a driver of the epithelial-mesenchymal transition (EMT), a process associated with cancer progression. Brachyury expression in human tumor cells enhances tumor invasiveness in vitro and metastasis in vivo, and induces resistance to various conventional therapeutics including chemotherapy and radiation. These characteristics, and the selective expression of brachyury for a range of human tumor types vs. normal adult tissues, make brachyury an attractive tumor target. Due to its intracellular localization and the "undruggable" character of transcription factors, available options to target brachyury are currently limited. Here we report on the development and characterization of an immunological platform for the efficient targeting of brachyury-positive tumors consisting of a heat-killed, recombinant Saccharomyces cerevisiae (yeast)-brachyury vector-based vaccine (designated as GI-6301) that expresses the full-length human brachyury protein. We demonstrate that human dendritic cells treated with recombinant yeast-brachyury can activate and expand brachyury-specific CD4+ and CD8+ T cells in vitro that, in turn, can effectively lyse human tumor cells expressing the brachyury protein. Vaccination of mice with recombinant yeast-brachyury is also shown here to elicit brachyury-specific CD4+ and CD8+ T-cell responses, and to induce anti-tumor immunity in the absence of toxicity. Based on these results, a Phase I clinical trial of GI-6301 is currently ongoing in patients with advanced tumors; to our knowledge, this is the first vaccine platform aimed at targeting a driver of tumor EMT that has successfully reached the clinical stage.

Combination therapy with a second-generation androgen receptor antagonist and a metastasis vaccine improves survival in a spontaneous prostate cancer model.

PURPOSE: Enzalutamide, a second-generation androgen antagonist, was approved by the U.S. Food and Drug Administration (FDA) for castration-resistant prostate cancer (CRPC) treatment. Immunotherapy has been shown to be a promising strategy for prostate cancer. This study was performed to provide data to support the combination of enzalutamide and immunotherapy for CRPC treatment. EXPERIMENTAL DESIGN: Male C57BL/6 or TRAMP (transgenic adenocarcinoma of the mouse prostate) prostate cancer model mice were exposed to enzalutamide and/or a therapeutic vaccine targeting Twist, an antigen involved in epithelial-to-mesenchymal transition and metastasis. The physiologic and immunologic effects of enzalutamide were characterized. The generation of Twist-specific immunity by Twist-vaccine was assessed. Finally, the combination of enzalutamide and Twist-vaccine to improve TRAMP mice overall survival was evaluated. RESULTS: Enzalutamide mediated immunogenic modulation in TRAMP-C2 cells. In vivo, enzalutamide mediated reduced genitourinary tissue weight, enlargement of the thymus, and increased levels of T-cell excision circles. Because no changes were seen in T-cell function, as determined by CD4(+) T-cell proliferation and regulatory T cell (Treg) functional assays, enzalutamide was determined to be immune inert. Enzalutamide did not diminish the ability of Twist-vaccine to generate Twist-specific immunity. Twist was confirmed as a valid tumor antigen in TRAMP mice by immunohistochemistry. The combination of enzalutamide and Twist-vaccine resulted in significantly increased overall survival of TRAMP mice compared with other treatment groups (27.5 vs. 10.3 weeks). Notably, the effectiveness of the combination therapy increased with disease stage, i.e., the greatest survival benefit was seen in mice with advanced-stage prostate tumors. CONCLUSIONS: These data support the combination of enzalutamide and immunotherapy as a promising treatment strategy for CRPC. Clin Cancer Res; 19(22); 6205-18. ©2013 AACR.

Maturation of human dendritic cells with Saccharomyces cerevisiae (yeast) reduces the number and function of regulatory T cells and enhances the ratio of antigen-specific effectors to regulatory T cells.

We compared the effects of yeast-treated human dendritic cells (DCs) with CD40L-matured human DCs for the induction of effector cells and the number and functionality of CD4(+)CD25(+)CD127(-)FoxP3(+) regulatory T cells (Tregs). DCs were treated with yeast or CD40L and cocultured with isolated autologous CD4(+) T cells. CD4(+)CD25(+)CD127(-) T cells isolated from the coculture of CD4(+) T cells plus yeast-treated DCs (yeast coculture) had a lower expression of FoxP3 and decreased suppressive function compared to CD4(+)CD25(+)CD127(-) T cells isolated from the coculture of CD4(+) T cells plus CD40L-treated DCs (CD40L coculture). Also, compared to the CD40L coculture, the yeast coculture showed increases in the ratio of CD4(+)CD25(+) activated T cells to Tregs and in the production of Th1-related cytokines (IL-2, TNF-α, IFN-γ) and IL-6. In addition, yeast-treated DCs used as antigen-presenting cells (APCs) incubated with the tumor antigen CEA enhanced the proliferation of CEA-specific CD4(+) T cells compared to the use of CD40L-matured DCs used as APCs. This is the first study to report on the role of yeast-treated/matured human DCs in reducing Treg frequency and functionality and in enhancing effector to Treg ratios. These results provide an additional rationale for the use of yeast as a vector in cancer vaccines.

Exploitation of differential homeostatic proliferation of T-cell subsets following chemotherapy to enhance the efficacy of vaccine-mediated antitumor responses.

The 5-year survival rate for stage IB-III non-small-cell lung cancer (NSCLC) remains 15%. Surgical resection followed by adjuvant chemotherapy with cisplatin and vinorelbine is one standard-of-care. We sought to determine in a preclinical model whether (a) the combination of cisplatin and vinorelbine could positively modulate components of the immune system independent of antitumor activity, and (b) there were synergistic effects of this drug combination and vaccine immunotherapy. We examined the effect of cisplatin/vinorelbine on gene expression, cell-surface phenotype, and CTL-mediated cytolysis of murine lung carcinoma cells in vitro; we also assessed the effects of cisplatin/vinorelbine on immune subsets and function of Tregs in vivo. Finally, we evaluated the potential synergy between chemotherapy and a recombinant yeast-CEA vaccine in a murine model transgenic for CEA with mice bearing lung tumors. These studies demonstrate that exposure of lung tumor cells to the platinum doublet cisplatin/vinorelbine modulates tumor cell phenotype and increases sensitivity to CTL-mediated cytolysis. These studies also demonstrate that cisplatin/vinorelbine (a) induces sub-myeloablative leucopenia that differentially modulates reconstitution of Treg versus effector T-cell subsets and (b) can be employed synergistically with vaccine, exploiting homeostatic peripheral expansion of T cells. Antitumor studies show for the first time that cisplatin/vinorelbine combined with vaccine increases the survival of mice with established NSCLC. These findings provide the rationale for the potential clinical benefit of the combined use of vaccine with cisplatin/vinorelbine chemotherapy regimens.

Mutation-specific control of BCR-ABL T315I positive leukemia with a recombinant yeast-based therapeutic vaccine in a murine model.

Chromosomal translocations generating the BCR-ABL oncogene cause chronic myeloid leukemia (CML) and a subset of acute lymphoblastic leukemia. The BCR-ABL(T315I) mutation confers drug resistance to FDA-approved targeted therapeutics imatinib mesylate, dasatinib, and nilotinib. We tested the ability of a recombinant yeast-based vaccine expressing the T315I-mutated BCR-ABL antigen to stimulate an anti-BCR-ABL(T315I) immune response. The yeast-based immunotherapy significantly reduced or eliminated BCR-ABL(T315I) leukemia cells from the peripheral blood of immunized animals and extended leukemia-free survival in a murine model of BCR-ABL(+) leukemia compared to animals receiving sham injection or yeast expressing ovalbumin. With immunization, leukemic cells harboring BCR-ABL(T315I) were selectively eliminated after challenge with a mixed population of BCR-ABL and BCR-ABL(T315I) leukemias. In summary, yeast-based immunotherapy represents a novel approach against the emergence of cancer drug resistance by the pre-emptive targeted ablation of tumor escape mutants.

Whole recombinant yeast-based immunotherapy induces potent T cell responses targeting HCV NS3 and Core proteins.

Control of primary infection with hepatitis C virus (HCV) is associated with robust and broad T cell immunity. In contrast, chronic infection is characterized by weak T cell responses suggesting that an approach that boosts these responses could be a therapeutic advance. Saccharomyces cerevisiae is an effective inducer of innate and adaptive cellular immunity and we have generated recombinant yeast cells (GI-5005) that produce an HCV NS3-Core fusion protein. Pre-clinical studies in mice showed that GI-5005 induced potent antigen-specific proliferative and cytotoxic T cell responses that were associated with Th1-type cytokine secretion. In studies in which GI-5005 was administered up to 13 times, no detectable vector neutralization or induction of tolerance was observed. Prophylactic as well as therapeutic administration of GI-5005 in mice led to eradication of tumor cells expressing HCV NS3 protein. Immunotherapy with GI-5005 is being evaluated in chronic HCV infected individuals in a Phase 1 clinical trial.

A comparison of entecavir and lamivudine for HBeAg-positive chronic hepatitis B.

BACKGROUND: Entecavir is a potent and selective guanosine analogue with significant activity against hepatitis B virus (HBV). METHODS: In this phase 3, double-blind trial, we randomly assigned 715 patients with hepatitis B e antigen (HBeAg)-positive chronic hepatitis B who had not previously received a nucleoside analogue to receive either 0.5 mg of entecavir or 100 mg of lamivudine once daily for a minimum of 52 weeks. The primary efficacy end point was histologic improvement (a decrease by at least two points in the Knodell necroinflammatory score, without worsening of fibrosis) at week 48. Secondary end points included a reduction in the serum HBV DNA level, HBeAg loss and seroconversion, and normalization of the alanine aminotransferase level. RESULTS: Histologic improvement after 48 weeks occurred in 226 of 314 patients in the entecavir group (72 percent) and 195 of 314 patients in the lamivudine group (62 percent, P=0.009). More patients in the entecavir group than in the lamivudine group had undetectable serum HBV DNA levels according to a polymerase-chain-reaction assay (67 percent vs. 36 percent, P<0.001) and normalization of alanine aminotransferase levels (68 percent vs. 60 percent, P=0.02). The mean reduction in serum HBV DNA from baseline to week 48 was greater with entecavir than with lamivudine (6.9 vs. 5.4 log [on a base-10 scale] copies per milliliter, P<0.001). HBeAg seroconversion occurred in 21 percent of entecavir-treated patients and 18 percent of those treated with lamivudine (P=0.33). No viral resistance to entecavir was detected. Safety was similar in the two groups. CONCLUSIONS: Among patients with HBeAg-positive chronic hepatitis B, the rates of histologic, virologic, and biochemical improvement are significantly higher with entecavir than with lamivudine. The safety profile of the two agents is similar, and there is no evidence of viral resistance to entecavir. (ClinicalTrials.gov number, NCT00035633.).