Introduction
Hepatitis B virus (HBV) infection is a major global public health concern. In 2019, the estimated global prevalence of chronic HBV infection was 4.1%, corresponding to 316 million infected people.1 Although a marked decline was seen in the prevalence of HBV across all ages and in children younger than 5 years of age between 1990 and 2019, the number of HBV-related deaths continues to increase.1 Most patients with chronic HBV infection maintain immune tolerance in their younger ages. However, once immune activation occurs, chronic hepatitis B (CHB) may progress into liver failure, cirrhosis, or hepatocellular carcinoma, which resulted in about 55,500 deaths globally per year.1,2
To date, four licensed nucleos(t)ide analogs are recommended for first line therapy in treatment of CHB in mainland China i.e., entecavir, tenofovir disoproxil fumarate (TDF), tenofovir alafenamide (TAF) and tenofovir amibufenamide (TMF; codename: HS-10234).3,4 They all have been shown to halt or even reverse disease progression.5,6 However, unless a functional cure is achieved, the anti-HBV treatment is generally life-long, which imposes high requirements for the efficacy and safety of these drugs.2 Among these, using entecavir may be restricted by the high proportion of lamivudine-experienced patients in mainland China,7–9 whereas the use of TDF is often complicated due to its bone and renal safety profile in an aging population.10–12 TAF, as an upgrade of TDF, has shown its noninferior efficacy and improved bone and renal safety in a general population. However, noninferiority of TAF regarding virological suppression was not established in patients with HBV DNA ≥7 or 8 log10 IU/mL for the first 96 weeks of treatments.
TMF, another prodrug of tenofovir, produced by ProTide technology,13 has structurally one more methyl group than TAF, which may lead to higher stability in peripheral blood and improved intracellular conversion. In vitro, TMF has a lower EC50 in HepG2.2.15 cells than TAF and TDF.14 In the reported 48-week results, TMF was statistically noninferior to TDF in antiviral efficacy, while displaying improved bone and renal safety. In June, 2021, TMF was approved in mainland China and was incorporated into the 2021 China National Reimbursement Drug List. In this report, we present the extended 96-week results of that study.
Results
Patient population
Among the 1,002 patients who received at least one dose of treatment, 666 were randomized in the TMF group and 336 in the TDF group. Of these, 605 (90.8%) and 297 (88.4%) completed the week 96 assessments, in the TMF and TDF groups. From week 48 to week 96, 62 patients discontinued early on (37 vs. 25 in the TMF and TDF group, respectively, as specified in Fig. 1). The median treatment duration was 96 weeks for both groups and over 99% of the patients had adherence ≥90% (no group difference observed, p=0.608). The baseline characteristics of the two treatment groups were well balanced and have been described in the week 48 report (also provided in Supplementary Table 1). The majority of patients were male (72.2%), with a median age of 35 years and interquartile range (IQR) of 29 to 44. The median level of HBV DNA titers was 7.31 (IQR: 5.86 to 8.23) log10 IU/mL with 38.0% being 8 log10 IU/mL and above. The percentage of patients with previously diagnosed cirrhosis was 19.5% for the HBeAg-positive population and 17.8% for the HBeAg-negative population. As for HBV treatment history, 6.6% of the pooled population had received interferon-based treatment before, and 28.5% of the patients had been treated with oral nucleos(t)ide analogs. The median non-indexed eGFR-epi and CrCl-cg values for patients at baseline were 111.70 mL/min and 114.85 mL/min, respectively. According to the ISCD standard, 12.0% of the subjects presented with osteopenia at baseline, and very few (0.9%) patients had osteoporosis. In the week 48 results, none of the patients had a persistent normal ALT and could be immune tolerant. The incidences of comorbidities, including diabetes, dyslipidemia, hypertension, cardiovascular diseases, upper respiratory tract infection, nasopharyngitis, hepatic steatosis, hyperuricemia, and hypertriglyceridemia were all even between two treatment groups.
Virological response
The primary efficacy endpoint at week 96 according to FAS is shown in Table 1. (see the per-protocol set results in Supplementary Table 2). In the HBeAg-positive population, 70.8% of patients in the TMF treatment group achieved HBV DNA <20 IU/mL, compared with 72.0% in the TDF treatment group (difference and 95% CI: −1.1%, −7.8% to 5.6%, p=0.746). In the HBeAg-negative population, the proportions of HBV DNA <20 IU/mL were 93.9% and 93.3% in the TMF and TDF groups respectively (difference: 0.4%; 95% CI: −5.8% to 6.7%; p=0.889). Both lower bounds of the 95% CI of the difference were above the predefined noninferiority margin. Similarly, there were no statistical differences in the proportion of patients achieving HBV DNA levels <29 IU/mL or <69 IU/mL between the two treatment groups, despite their HBeAg status. The mean decline of HBV DNA titers from baseline to week 96 was similar in the TMF and TDF groups (Supplementary Fig. 1; HBeAg-positive patients: −6.38 log10 IU/mL vs. −6.42 log10 IU/mL, p=0.795; HBeAg-negative patients: −6.08 log10 IU/mL vs. −5.78 log10 IU/mL, p=0.279). In the HBeAg-positive population, the proportions of patients with undetectable HBV DNA at week 96 were 21.0% and 21.1% in the TMF and TDF groups, respectively (difference; −0.1%; 95% CI: −6.3% to 6.0%; p=0.970), while the proportions of patients in the HBeAg-negative population were 48.3% and 41.1% (difference: 7.4%; 95% CI: −5.2% to 19.9%; p=0.253).
Table 1Primary and secondary efficacy endpoints at week 96 in the full-analysis set
| HBeAg-positive
| HBeAg-negative
|
|---|
| TMF 25 mg (N=486) | TDF 300 mg (N=246) | Difference (95% CI) | p-value | TMF 25 mg (N=180) | TDF 300 mg (N=90) | Difference (95% CI) | p-value |
|---|
| HBV DNA <20 IU/mL | 344/486 (70.8) | 177/246 (72.0) | −1.1 (−7.78, 5.55) | 0.746 | 169/180 (93.9) | 84/90 (93.3) | 0.4 (−5.77, 6.66) | 0.889 |
| HBV DNA <29 IU/mL | 363/486 (74.7) | 194/246 (78.9) | −4.1 (−10.31, 2.07) | 0.204 | 170/180 (94.4) | 84/90 (93.3) | 1.0 (−5.16, 7.14) | 0.748 |
| HBV DNA <69 IU/mL | 406/486 (83.5) | 211/246 (85.8) | −2.2 (−7.63, 3.21) | 0.435 | 173/180 (96.1) | 85/90 (94.4) | 1.5 (−4.00, 7.06) | 0.569 |
| HBeAg lossa | 129/478 (27.0) | 59/246 (24.0) | 3.2 (−3.35, 9.68) | 0.349 | − | − | − | − |
| HBeAg seroconversionb | 63/417 (15.1) | 26/206 (12.6) | 2.5 (−3.16, 8.19) | 0.399 | − | − | − | − |
| HBsAg lossc | 1/486 (0.2) | 1/246 (0.4) | NC | NC | 2/180 (1.1) | 0/90 (0.0) | NC | NC |
| Mean ALT change from baseline (SD) | −108.7 (113.8) | −95.7 (116.4) | −7.4 (−13.50, −1.34) | 0.017 | −96.9 (108.1) | −83.2 (106.4) | −3.1 (−8.32, 2.08) | 0.238 |
| ALT normalization rated | 356/479 (74.3) | 154/242 (63.6) | 10.7 (3.45, 17.90) | 0.003 | 129/173 (74.6) | 59/86 (68.6) | 6.0 (−5.99, 17.92) | 0.315 |
| Meane FIB-4 score change from baseline (SE) | −0.51 (0.03) | −0.40 (0.04) | −0.1 (−0.18, −0.02) | 0.013 | −0.96 (0.10) | −0.84 (0.11) | −0.12 (−0.29, 0.04) | 0.144 |
| Meane LSM value change from baseline (SE) | −3.71 (0.14) | −4.05 (0.19) | 0.34 (−0.09, 0.77) | 0.118 | −3.76 (0.46) | −4.15 (0.50) | 0.38 (−0.39, 1.16) | 0.328 |
Among the HBeAg-positive patients, 164 had observed treatment failure (i.e., finished the week 96 visit and had an HBV DNA >20 IU/mL or virological breakthrough at any visit) that 111 received TMF (22.8%) and 53 received TDF (21.5%). Among those, there was a similar proportion of patients with viral loads ≥20 IU/ml and <69 IU/ml in the TMF group (52.3%) and the TDF group (56.6%). For the remaining patients with HBV DNA >69 IU/mL, 49 receiving TMF and 19 receiving TDF had plateaus of viral loads (decrease <1 log10 IU/mL from week 48 to week 96). In the HBeAg-negative population, only eight patients receiving TMF and no patients receiving TDF had observed treatment failure at week 96 visit.
Twenty-two patients (2.2%) had virological breakthrough in each group during 96 weeks of treatment. Hereinto, eight patients in the TMF group developed virological breakthrough after week 48, compared with five patients in the TDF group. All 22 patients underwent gene sequencing for resistance test. Only one patient in the TMF group was found to have mutations on rtv173L, rtL180M, and rtM204V which were consistently detected at baseline and week 48.
As for subgroup analysis defined by baseline characteristics, the primary efficacy endpoint showed no significant interactions in HBeAg-positive or negative populations by FAS and per-protocol set (Supplementary Figs. 2 and 3 and Supplementary Table 3). Hereinto, the noninferiority of virological suppression was also seen in subsets of patients with high viral load at baseline. For patients with HBV DNA ≥7 log10 IU/mL, the CMH adjusted differences between TMF and TDF treatment groups were 0.8% (95% CI: −7.70% to 9.24%, p=0.859) or 11.7% (95% CI: −10.50% to 33.83%, p=0.239) in HBeAg-positive or -negative populations, respectively. As the lower bound of the 95% CIs did not exceed the margin of −12%, the noninferiority was established, which is a similar case in subgroups of patients with HBV DNA ≥8 log10 IU/mL.
Serological response and HBsAg dynamics
Among patients who were HBeAg-positive at baseline, 27.0% achieved HBeAg loss at week 96 in the TMF arm, compared with 24.0% in the TDF controls (p=0.349 for group difference). Among patients who were seropositive for HBeAg and negative for anti-HBe at baseline, 15.1% achieved HBeAg seroconversion in the TMF group and 12.6% in the TDF controls respectively (p=0.399 for group difference). At week 96, totally four patients achieved HBsAg loss (three in the TMF group and one in the TDF group), but none achieved HBsAg seroconversion. The post-hoc analysis of serum HBsAg dynamics was provided (Supplementary Table 4). In the HBeAg-positive population, the mean declines at week 96 in the TMF group and TDF group were −0.28±0.926 (SD) and −0.30±0.892 log10 IU/mL, respectively (p<0.001 in both groups). The changes were not significant from week 48 to week 96, and the intergroup difference was not significant at each time point. A numerically higher proportion of patients with a ≥1 log10 IU/mL decline were seen in the TMF group that TDF group (18.4% vs. 13.3%, p=0.104).
In the HBeAg-negative population, the mean declines at week 96 in the TMF group and TDF group were −0.43±0.749 (SD) and −0.34±0.372 log10 IU/mL, respectively. The declines were significant from week 48 to week 96, while the intergroup difference was not significant at each time point. The proportion of patients with a ≥1 log10 IU/mL decline were similar in the TMF group and TDF group (9.9% vs. 8.8%, p=0.995).
ALT response and fibrosis regression
For the pooled population, the TMF group achieved a nearly 10% greater ALT normalization rate (74.4% vs. 64.9%, p=0.002) and a significantly larger mean reduction in ALT levels from baseline to week 96 (−105.5 U/L vs. −92.4 U/L, p=0.009). In the HBeAg-positive population, patients in the TMF group had a significantly higher ALT normalization rate at week 96 compared with patients in the TDF group (74.3% vs. 63.6%, p=0.003; Table 1), and greater mean reduction in ALT levels from baseline (−108.7 U/L vs. −95.7 U/L, p=0.017; Table 1). Furthermore, patients in the TMF group had higher rates of ALT normalization since week 24, and the superiority was maintained up to week 96 (p=0.003) (Supplementary Fig. 4). In the HBeAg-negative population, the ALT normalization rate and the ALT decline from baseline were only numerically higher in the TMF group than that in the TDF group.
Values of liver stiffness measure (LSM) and fibrosis-4 (FIB-4) scores decreased significantly from baseline to week 96 in both treatment groups (Supplementary Tables 5 and 6). The decrease in LSM at week 96 from baseline was not significantly different between these two groups, either in HBeAg-positive (p=0.118) or negative population (p=0.328). For the FIB-4 score of HBeAg-positive patients, a significantly greater decline was seen in patients receiving TMF than that in TDF (−0.51±0.03 vs. −0.40±0.04, p=0.013). This significant intergroup difference was not observed in the HBeAg-negative populations.
General safety
After 96 weeks of treatment, both treatment groups were well tolerated regarding their general safety (Table 2). Most adverse events were mild to moderate in severity. Only one case of study drug-related serious adverse event (SAE) was seen in the TDF group. The incidence of grade ≥3 study drug-related adverse events (AEs) was low and distributed equally in two groups (6.3% in the TMF group and 6.8% in the TDF group). Three patients in the TMF group paused the treatment and only one was due to study drug-related AEs. Five patients in each group had permanent study drug discontinuation and only two of the five instances in the TDF group were associated with study drug-related AEs. Specifically, adverse events with an incidence of ≥5% were upper respiratory tract infection (216 [32.4%] patients receiving TMF vs. 96 [28.6%] patients receiving TDF), hepatic steatosis (92 [13.8%] vs. 30 [8.9%]), hyperuricemia (89 [13.4%] vs. 29 [8.6%]), hypophosphatemia (85 [12.8%] vs. 40 [11.9%]), nasopharyngitis (64 [9.6%] vs. 32 [9.5%]) and hypertriglyceridemia (51 [7.7%] vs. 12 [3.6%]). The most frequent grade ≥3 adverse events were abnormal investigations of serum ALT and aspartate aminotransferase (AST) levels, which mainly occurred within 48 weeks.
Table 2Safety of TMF and TDF at week 96
| n (%)
|
|---|
| TMF 25 mg (N=666) | TDF 300 mg (N=336) |
|---|
| Patients with any adverse event | 640 (96.1) | 311 (92.6) |
| Study drug-related AE | 371 (55.7) | 211 (62.8) |
| Patients with SAE | 68 (10.2) | 33 (9.8) |
| Study related SAE | 0 (0.0) | 1 (0.3) |
| Patients with grade 3 and above AE | 168 (25.2) | 80 (23.8) |
| Patients with study drug-related AE ≥ grade 3 | 42 (6.3) | 23 (6.8) |
| AE leading to study drug interruption | 3 (0.5) | 0 (0.0) |
| AE leading to study drug permanent discontinuation | 5 (0.8) | 5 (1.5) |
| Patients with any AE in ≥5% patients | 575 (86.3) | 281 (83.6) |
| Laboratory abnormality | 385 (57.8) | 213 (63.4) |
| Alanine aminotransferase increased | 176 (26.4) | 89 (26.5) |
| Aspartate aminotransferase increased | 125 (18.8) | 74 (22.0) |
| Blood parathyroid hormone increased | 93 (14.0) | 48 (14.3) |
| Blood creatine phosphokinase increased | 64 (9.6) | 34 (10.1) |
| Bone density decreased | 43 (6.5) | 43 (12.8) |
| Weight decreased | 43 (6.5) | 43 (12.8) |
| Blood bilirubin increase | 52 (7.8) | 19 (5.7) |
| Gamma−glutamyl transferase increased | 48 (7.2) | 22 (6.5) |
| Total bile acids increased | 40 (6.0) | 21 (6.3) |
| Weight increased | 40 (6.0) | 9 (2.7) |
| Platelet counts decreased | 30 (4.5) | 17 (5.1) |
| Infection and infestations | 298 (44.7) | 141 (42.0) |
| Upper respiratory tract infection | 216 (32.4) | 96 (28.6) |
| Nasopharyngitis | 64 (9.6) | 32 (9.5) |
| Urinary tract infection | 48 (7.2) | 27 (8.0) |
| Pharyngitis | 30 (4.5) | 18 (5.4) |
| Metabolism and nutrition disorders | 196 (29.4) | 72 (21.4) |
| Hypophosphatasemia | 85 (12.8) | 40 (11.9) |
| Hyperuricemia | 89 (13.4) | 29 (8.6) |
| Hypertriglyceridemia | 51 (7.7) | 12 (3.6) |
| Hyperlipidemia | 34 (5.1) | 2 (0.6) |
| Hepatobiliary disorders | 121 (18.2) | 43 (12.8) |
| Hepatic steatosis | 92 (13.8) | 30 (8.9) |
| Gallbladder polyps | 34 (5.1) | 17 (5.1) |
| Gastrointestinal disorders | 96 (14.4) | 42 (12.5) |
| Diarrhea | 46 (6.9) | 14 (4.2) |
| Toothache | 34 (5.1) | 15 (4.5) |
| Abdominal pain | 22 (3.3) | 17 (5.1) |
| Respiratory, thoracic, and mediastinal disorders | 48 (7.2) | 15 (4.5) |
| Cough | 48 (7.2) | 15 (4.5) |
| Renal and urinary disorders | 36 (5.4) | 23 (6.8) |
| Proteinuria | 36 (5.4) | 23 (6.8) |
| Blood and lymph disorders | 15 (2.3) | 24 (7.1) |
| Anemia | 15 (2.3) | 24 (7.1) |
Safety of special interest: renal and bone abnormalities
Renal safety results at week 96 are shown in Table 3. At week 96, a significantly smaller decrease in the median of CrCl-cg was seen in patients receiving TMF compared with patients receiving TDF (−3.01 mL/min vs. −6.65 mL/min, respectively, p<0.001). A similar difference was seen for non-indexed eGFR-epi (−1.68 mL/min vs. −3.12 mL/min for TMF vs. TDF, p=0.010). Moreover, there were significantly fewer patients with a ≥10% sustained decline of non-indexed eGFR-epi from baseline in the TMF group compared with the TDF group (6.0% vs. 11.0%, TMF vs. TDF, p=0.005). The incidences of de novo hypophosphatemia were similar between the two groups, but patients in the TMF group had a lower incidence of elevated serum PTH at week 96 (10.0% vs. 16.9%, p=0.005). Only one patient in the TDF group had developed clinically diagnosis of renal tubular dysfunction, and the deterioration of proteinuria was uncommon and even in each group. None of the patients in the TMF and TDF group experienced adverse events of proximal tubulopathy or adverse renal events, resulting in discontinuation of the study drugs. Two patients in the TMF group reported serious adverse events of renal and urinary disorders, which were obstructive nephropathy and renal hydrocele.
Table 3Renal safety outcomes at week 96
| TMF 25 mg (N=666) | TDF 300 mg (N=336) |
|---|
| CrCl (mL/min) | | |
| Baseline | | |
| Median [q1, q3] | 115.51 (100.03,135.62) | 114.33 (97.44,132.54) |
| Change at week 96 | | |
| Median [q1, q3] | −3.01 (−13.24,7.27) | −6.65 (−15.70,2.81) |
| Least squares mean (SE)* | −2.75 (0.76) | −6.71 (0.99) |
| Nonindexed eGFR (mL/min) | | |
| Baseline | | |
| Median [q1, q3]) | 111.73 (101.91,123.51) | 111.47 (100.53,121.25) |
| Change at week 96 | | |
| Median [q1, q3] | −1.68 (−8.00,3.27) | −3.12 (−9.83,1.72) |
| Least squares mean (SE)* | −2.35 (0.45) | −4.07 (0.59) |
| Sustained decline of nonindexed eGFR at week 96* (≥10%) | 40 (6.0%) | 37 (11.0%) |
| De novo hypophosphatemia (<2.5 mg/dL) | 46 (7.6%) | 22 (7.1%) |
| De novo PTH elevation* | 54 (10.0%) | 48 (16.9%) |
| Clinical diagnosis of renal tubular dysfunction† | 0 | 1 (0.3%) |
| Deterioration of proteinuria | 22 (3.3%) | 10 (3.0%) |
The bone safety profile was assessed in pooled population. As for the BMD at week 96, the mean percentage change from baseline for all three measurement spots remained significantly different, with a greater decrease in the TDF group (Fig. 2 and Table 4). From week 48 to week 96, significant declines were seen at hip and femur neck in patients receiving TDF, of which the least square mean declines were −0.39±0.199% and −0.95±0.253%, respectively (all p<0.05). For patients receiving TMF, only the BMD at femur neck significantly declined from week 48, of which the least square mean decline was −0.43±0.193% (p<0.001). In contrast, there were significantly fewer patients in the TMF group experiencing a >5% decrease in BMD from baseline at femur neck, total hip or lumbar spine (L1-L4). There was no statistically significant difference in the incidences of osteopenia and osteoporosis diagnosed by ISCD standard between two treatment groups. From week 48 to week 96, only nine patients experienced a bone fracture, of whom seven received TMF and two others received TDF. However, none were fragility fractures.
Table 4Bone safety outcomes at week 96
| TMF 25 mg (N=666) | TDF 300 mg (N=336) | p-value* for intergroup comparison |
|---|
| Mean percentage change in BMD from baseline (SD) |
| Hipa | −0.44 (4.104) | −2.47 (4.206) | <0.001 |
| Femur necka | −0.42 (5.258) | −2.57 (5.075) | <0.001 |
| Spine (L1-L4)b | 0.04 (7.291) | −2.13 (4.109) | <0.001 |
| Mean percentage change in BMD from week 48 (SD) |
| Hip | 0.05 (3.393) | −0.38 (3.208) | 0.032 |
| (Intragroup p-value) | 0.66 | 0.01 | |
| Femur neck | −0.49 (4.418) | −0.95 (3.892) | 0.074 |
| (Intragroup p-value) | <0.001 | <0.001 | |
| Spine(L1-L4) | −0.01 (6.388) | −0.19 (3.182) | 0.69 |
| (Intra−group p-value) | 0.14 | 0.41 | |
| Incidences of >5% decline in BMD from baseline |
| Hipa | 62 (9.6%) | 69 (21.3%) | <0.001 |
| Femur necka | 95 (14.7%) | 90 (27.8%) | <0.001 |
| Spine (L1-L4)b | 65 (10.0%) | 56 (17.1%) | 0.001 |
| De novo osteopenia† | 22/573 (3.8%) | 18/294 (6.1%) | 0.124 |
| De novo osteoporosis‡ | 2/47 (4.3%) | 5/32 (15.6%) | 0.115 |
The adverse impact on bone turnover biomarkers at week 96 was also assessed (Supplementary Tables 7 and 8). As for bone absorption, patients in the TMF group had a mean percentage change of +8.26% in serum c-type collagen sequence levels, but patients in the TDF group had a 39.14% increase (p<0.001 for group difference) from baseline to week 96. In terms of bone formation, the serum level of procollagen type 1 N-terminal propeptide decreased by 13% in the TMF group and increased by 3.9% in the TDF group (p<0.001 for group difference).
Safety of special interest: metabolic abnormalities
At week 96, a significantly larger decline in the levels of all serum lipid parameters from baseline was seen in the TDF group than that in the TMF group (Fig. 3), while a significantly lower increase in the total cholesterol/high-density lipoprotein (TC/HDL) ratio was seen correspondingly. However, the median changes from week 48 to week 96 were mild for all parameters in each group (Table 5). In the TDF group, none of the serum lipid parameters, except for the TC/HDL ratio, changed significantly from week 48 onward. For the TMF group, a mild median (IQR) change of −0.02 (−0.14, 0.07) mmol/L in HDL, and 0.05 (−0.21, 0.38) in TC/HDL ratio were seen with statistical significance. Besides, the intergroup differences were significant for the change of HDL levels only. Cardiovascular diseases (CVDs) related AEs were reviewed, although they were rare events (Supplementary Table 9). No apparent difference in the incidence rate was seen. Only a single case of cardiomyopathy, cerebral venous sinus thrombosis, cardiomyopathy, or myocardial ischemia was seen in the TMF group.
Table 5Change of metabolic parameters in each group from week 48 to week 96
| Intergroup comparison | p-value |
|---|
TMF 25 mg (N=666)
| TDF 300 mg (N=336)
|
|---|
| Median (q1, q3) | p-value | Median (q1, q3) | p-value |
|---|
| TC (mmol/L) | −0.04 (−0.36, 0.31) | 0.052 | 0 (−0.27, 0.29) | 0.415 | 0.056 |
| LDL (mmol/L) | 0.02 (−0.27, 0.30) | 0.095 | 0 (−0.21, 0.24) | 0.343 | 0.592 |
| HDL (mmol/L) | −0.02 (−0.14, 0.07) | <0.001 | 0 (−0.10, 0.08) | 0.303 | 0.031 |
| TC/HDL | 0.05 (−0.21, 0.38) | <0.001 | 0.02 (−0.19, 0.34) | 0.012 | 0.395 |
| TG (mmol/L) | 0 (−0.25, 0.32) | 0.282 | 0 (−0.18, 0.19) | 0.961 | 0.586 |
| Weight (kg) | 0.30 (−1.00, 2.00) | <0.001 | 0.00 (−1.00, 1.50) | 0.378 | <0.001 |
Consistent with week 48, patients in the TMF treatment group continued to gain weight at week 96 (a median increase of 1.0 [IQR −1.00, 3.10] kg from baseline, p<0.001; a median increase of 0.30 [IQR −1.00, 2.00] kg from week 48, p<0.001). In contrast, the TDF group did not maintain a significant weight loss at week 96 compared with week 48 (p=0.378), while the group difference was still significant (p<0.001).
Discussion
We have previously reported that TMF had noninferior efficacy and improved safety profiles compared with TDF through the first 48-week treatment of this large, randomized, double-blind, phase III trial in mainland China. However, overall virological suppression rate was relatively low in each group and the short follow-up duration may not have been sufficient for safety assessments. Here, we presented the results of 96 weeks of treatment with TMF in a double-blind, active control setting.
At week 96, the virological response rate of each group continued to show noninferiority between the TMF and TDF therapy, either in the HBeAg-positive or negative populations. Prespecified subgroup analyses revealed no significant difference in virological suppression. In patients with baseline HBV DNA >7 log10 IU/mL or >8 log10 IU/mL, TMF also established noninferior efficacy over TDF. With a larger pooled sample size in its phase III trials, TAF did not establish the noninferior efficacy in this subgroup of patients.20 For HBeAg-positive population at week 48, 50.2% of patients in the TMF group and 53.7% of patients in the TDF group achieved HBV DNA <20 IU/mL, which are both lower than expected. With prolonged treatment, about 20% more patients in each group achieved virological response at week 96. For those who did not achieve HBV DNA <20 IU/mL at week 96, over 52% have HBV DNA titers lower than 69 IU/mL. Hence, more patients could be expected to achieve virological response with further treatment.
The proportion of HbeAg seroconversion and HbeAg loss were similar in the two treatment groups at week 96. From week 48 to week 96, the proportion of HbeAg seroconversion increased from 9.4% to 15.1% in the TMF group and 8.3% to 12.6% in the TDF group. In terms of HbsAg, comparable declines were seen in the two treatment groups up to week 96. Further analysis showed that the mean reduction of qHBsAg were numerically larger in HBeAg-negative patients than that in HBeAg-positive ones at week 96, which is not under the previous understanding of HbsAg dynamics.21,22 The lower serum ALT levels at baseline in the HBeAg-positive patients compared with previous studies may be one of the possible answers.22 A further decline from week 48 to week 96 in HBeAg-negative population was another uncommon situation. Though only four patients achieved HbsAg loss during 96 weeks of treatment, over 34% of the HBeAg-positive patients and 20% of the HBeAg-negative patients achieved a ≥0.5 log10 IU/mL decline of serum HbsAg and almost half of them experienced a ≥1 log10 IU/mL decline, which was predictive for HbsAg loss.22
At week 48, more patients in the TMF group achieved ALT normalization than those in the TDF group. This superior effect of TMF over TDF continued through 96 weeks of treatment, confirming that TMF had a durable advantage over TDF in terms of ALT normalization. In this week 96 analysis, the rate of ALT normalization was significantly higher in the pooled patients receiving TMF than in those receiving TDF. The findings in the HBeAg-positive patients (74.3% vs. 63.6%) followed those in the pooled patients. For HBeAg-negative patients, the ALT normalization rate showed no statistical difference between TMF and TDF at week 96. HbeAg-negative patients receiving TAF treatment had a significantly higher ALT normalization rate than those receiving TDF in its phase III trials. The discrepancy between the TMF study and the TAF study may be related to the less strict criteria of ALT normalization and higher baseline ALT levels in our study. As for other efficacy endpoints, significant differences were not observed between treatment arms other than the reduction in the FIB-4 score among HBeAg-positive patients. As expected, the incidences of serological responses increased with prolonged treatment duration in all groups.
In general safety, both 25 mg TMF and 300 mg TDF were well tolerated at week 96. Similar incidences of AE and SAE were seen in the two groups. From week 48 to week 96, the proportions of patients who had at least one AE, AE ≥ grade 3, or SAE increased evenly in each group by around 5–7%.15 Hereinto, study-drug related cases only accounted for a small proportion and there were no new study drug-related SAEs after week 48. For AEs reported by investigators, patients in the TMF group were seen to have slightly higher incidences of weight increased, hyperuricemia, hypertriglyceridemia, hyperlipidemia, hepatic steatosis and diarrhea and slightly lower incidences of weight decrease, proteinuria, abdominal pain, and anemia than those in the TDF group.
The major safety concerns of the long-term use of TDF are renal toxicity and reductions of BMD. Our previous results at week 48 showed that patients who received TMF had better bone and renal safety. In the present report, these benefits persisted. As for renal function, there were significantly fewer declines of eGFR-epi and CrCl-cg in patients receiving TMF than that in patients receiving TDF at week 96. Specifically, patients receiving TMF had a median decline of 3.01 mL/min in CrCl-cg, compared with 6.65 mL/min in patients receiving TDF. The amount of intergroup difference seems smaller than that was reported by TAF trials.20 However, the Cockcroft-Gault equation was developed to estimate the clearance rate of creatinine, which usually over-estimates the GFR.17 The eGFR calculated by the CKD-EPI equation was recommended among individuals with normal or only mildly reduced GFR.23,24 On the other side, the change of body weight exhibited a opposite trend between the two treatment arms, indicating that the traditional eGFR indexed to body surface area may not be appropriate.25 With the non-indexed unit, the decline of eGFR seemed milder in both treatment arms (−1.68 mL/min for TMF, −3.12 mL/min for TDF). However, the intergroup difference in eGFR decline still remained significant, and 5% more patients presented with a ≥10% sustained decline of eGFR-epi in the TDF group (p=0.005). Besides, patterns of kidney injury due to TDF also include proximal tubular dysfunction.26–28 In our study, only one patient in the TDF group presented with a clinical diagnosis of renal tubular dysfunction. Hypophosphatasemia in TDF-treated patients is usually considered a sign of renal tubular damage, however, the incidence of de novo hypophosphatemia was even in each group. Notably, a significantly higher incidence of serum PTH level elevation was seen in the TDF group over TMF group. Given that hypophosphatemia is actually the result of PTH elevation secondary to calcium loss by the renal tubular damage,29–32 the PTH elevation may be a more straightforward sign of underlying tubular dysfunction. As described above, TMF may cause lower levels of eGFR decline and less tubular damage than TDF.
Like renal findings, a smaller percentage decline of BMD from baseline to week 96 was seen in patients receiving TMF than that in patients receiving TDF. This result continued to support the improved bone safety of TMF over TDF, either in hip, femur neck, or lumbar spine. Though not common in each group, when compared with TMF group, numerically higher incidences of de novo osteopenia or osteoporosis were still seen in the TDF group than TMF group. Besides, there were more patients in the TDF group experienced a >5% decline of BMD than patients in the TDF group (7.1–13.1% at different spots), which was more reflective of a higher risk of fragility fractures. Of note, in patients receiving TDF, the amount of BMD decline from week 48 to 96 was much lower than from baseline to week 48, and the intergroup difference was significant only regarding the hip. According to the 144-week comparison of TAF and TDF, the BMD loss of TDF treatment did not further enlarge since week 48 at the spine and week 96 at the hip.33–36 Hence, it is reasonable to speculate that the bone loss mainly occurred in the first or second year of TDF treatment.
Although having renal or osteal toxicity in some patients, TDF treatment was found to have a lipid or weight lowering effect, which was firstly described in HIV infected patients.33–35 In the week 48 results of our study, levels of fasting TC, LDL, HDL, and weight were all significantly reduced by TDF therapy. Hence, TMF therapy seems to have a plausible higher incidence of metabolism and nutrition disorder and hepatic steatosis than TDF therapy. However, none of the fasting lipid parameters significantly changed from week 48 to week 96 in the TDF group. Similarly, the change of lipid parameters in patients receiving TMF was mild from week 48 to week 96 that significantly change was only seen in HDL by a median 0.02 mmol/L decrease. Besides, like the findings at week 48, we did not observe significant differences in the incidences of cardiovascular diseases between two treatment arms at week 96. Hence, we consider that long-term TMF treatment will have a neutral effect on serum lipids. Indeed, other studies observed a stable profile of lipid parameters for 5-year treatment of TAF or in previously entecavir treated patients after switching to TAF.36,37
A median weight gain of 0.3 kg was seen in the TMF group from week 48 to week 96, which is much lower than that from baseline to week 48. Weight gain is a common condition in CHB patients after virological suppression.38,39 As reported by the same study mentioned above, weight decrease was seen after switching to TAF for 48 weeks in patients treated by entecavir, compared with weight increase in patients previously treated by TDF. This result further confirmed the weight lowering effect of TDF, rather than weight increasing by TAF or TMF treatment. Because of these points, weight gained in patients receiving TMF should not be a major safety concern either.
There are several limitations in this trial. First, the enrolled patients in this trial were relatively young, but we are facing an older CHB population in real-world with increasing comorbidities like bone and renal disorders.40 Therefore, the significantly higher incidence of bone and renal toxicity of TDF over TMF may still be underestimated in our study. Also, the hyperlipidemia usually correlates with ALT elevation. Hence, the second limitation lies because we did not carry out multivariate analysis toward ALT normalization, especially considering that a higher incidence of hyperlipidemia was seen in the TMF group. It is reasonable to carry out deeper investigations toward ALT normalization soon. Last but not the least, considering the requirement of long-term suppression of HBV, the efficacy and safety results of 96 weeks may still be insufficient. Hence, this study has been extended into a 10-year real-world follow-up study. After 96 weeks of treatment, TMF maintained similar effectiveness in viral suppression to TDF with significantly less bone and renal toxicity.