Hideki Mori, Hidekazu Suzuki

Abstract Third generation of quinolones, such as levofloxacin and moxifloxacin, -containing regimens are often used in second-line or rescue treatment of Helicobacter pylori infection. However, the increasing antibiotic resistance to quinolones affects the efficacies of quinolones-containing therapies in recent years. Therefore, there is a need to enhance the effectiveness of quinolonescontaining therapies. Sitafloxacin, a fourth-generation quinolone, and vonoprazan, a novel potassium-competitive acid blocker, are now available as more effective treatment options. The aim of this paper is to summarize the current evidence of quinolone-containing therapies in rescue treatments, and to discuss the importance of drug sensitivity tests or analysis of gyrA mutation before treatments.

Key words: Helicobacter pylori; Levofloxacin; Sitafloxacin; Moxifloxacin; gyrA;Vonoprazan

INTRODUCTION

Helicobacter pylori(H. pylori) is closely related to gastric cancer, gastric ulcer, atrophic gastritis, mucosa-associated lymphoid tissue lymphoma, andH. pylori-associated dyspepsia. Thus, eradication ofH. pyloriis useful for treatment and prevention of these diseases[1-6]. In recent years, eradication ofH. pylorihas become difficult due to an increase in antibiotic resistance, thereafter selection of an efficient regimen has become increasingly important[1,7].

Levofloxacin-containing regimens are used as rescue therapy in many countries.However, in recent times, levofloxacin-amoxicillin-proton pump inhibitor (PPI)regimens were shown to be insufficient forgyrAmutation positiveH. pyloristrains.Moreover, prevalence of quinolone resistance combined with increasedgyrAmutation positive strains have reduced the effectiveness of levofloxacin-amoxicillin-PPI regimen.

In recent years, the high effectiveness of sitafloxacin, a fourth-generation quinolone,-containing regimens togyrAmutation positiveH. pyloristrains, has been demonstrated[8,9]. At this time, this article only reported the use of sitafloxacincontaining regimen in Japan. However, sitafloxacin will likely be the main quinolonecontaining treatment in the future.

Vonoprazan, a novel potassium-competitive acid blocker which has a strong acid secretion inhibitory effect, has been available since 2015. The high efficacy of vonoprazan as first- and second-lineH. pylorieradication therapy treatment has already been shown[10,11]. Thus, vonoprazan is expected to play a role in quinolonecontaining rescue therapies.

In this article, we describe the current status of quinolone-containing rescue therapies.

STATUS OF QUINOLONE-CONTAINING RESCUE THERAPIES IN THE WORLD’S GUIDELINES

We reviewed guidelines from the United States (2017), Europe (2016), Canada (2016),China (2016) and Japan (2016)[7,12-14]. Only the guideline from America suggested levofloxacin-containing triple therapy consisting of a PPI, levofloxacin, and amoxicillin as a first-line treatment option[12]. The basis of this recommendation was a network meta-analysis that showed levofloxacin-containing triple therapy for 10-14 d proved superior to clarithromycin-containing triple therapy for 7 d (90%, 95%CI: 84%-94%vs73%, 95%CI: 71%-75%; RR 1.23, 95%CI: 1.16–1.29)[15]. The guidelines in the United States, Europe, Canada and China recommended levofloxacin-containing triple regimen as a rescue therapy[1,7,12,13]. The guidelines in Canada and China stated that increasing resistance rate of quinolones might affect the eradication rate, hence it did not recommend levofloxacin-containing regimen to be used as an initial treatment. The Japanese guideline of 2009 suggested levofloxacin-containing triple therapy as a third-line treatment option[16]. However, the 2016 guideline for Japan suggested sitafloxacin-containing triple therapy consisting of a PPI, sitafloxacin, and amoxicillin as a third-line treatment option[14]. Levofloxacin triple therapy was no longer recommended in Japan.

IMPORTANT ROLE OF GYRA MUTATION FOR RESISTANCE TO QUINOLONES

The most common mechanism of high-level fluoroquinolone resistance is due to mutation in one or more of the genes that encode the primary and secondary targets of these drugs, the type II topoisomerases (gyrA, gyrB, parCandparE)[17].

Mutations ofgyrAwithin the quinolone resistance-determining regions have been found to be the main mechanism for quinolone resistance inH. pylori. The position of thegyrAmutation is usually limited to N87 or D91, both of which are in the DNAbinding region on the N-terminal domain of thegyrAprotein, which includes fluoroquinolone-binding sites[18,19].gyrAmutations inH. pyloristrains correlate with phenotypic resistance of levofloxacin and sitafloxacin[8,20]. Liouet al[20]concluded thatgyrAmutation inH. pyloristrains is a better marker than phenotypic resistance in the prediction of levofloxacin-containing treatment outcomes[20]. We also showed that the presence ofgyrAmutation is a more sensitive marker of eradication failure compared to minimum inhibitory concentrations (MICs) of sitafloxacin in using sitafloxacincontaining regimen[8]. In fact, the eradication rates ofgyrAmutation-positive strains were around 70% with sitafloxacin-containing regimen, whereas most of all strains withoutgyrAmutation can be eradicated[9]. In meta-analysis, we found that the relative risk of the eradication failure is significantly lower ingyrAmutation at D91 compared togyrAmutation at N87[9]. The MICs of double-mutated strains were extremely higher than those of single-mutated strains[19].

gyrBis unlikely to mutate and is thought to have little resistance[21,22], but some reports have reported resistance due togyrB[23,24]. Since neitherparCnorparEis found in the complete gene sequences ofH. pylori, it is thought to be not involved in resistance[25,26].

EPIDEMIOLOGY OF RESISTANCE TO QUINOLONES IN H.PYLORI

The prevalence of primary resistance ofH. pylorito levofloxacin has been reported to range from 11.0% to 62.2% in different countries (Figure 1)[21,27-35]. There is no relationship between geographic factor and the resistance to levofloxacin. These data suggested that acquisition of resistance is related to high consumption rate of quinolones. Thus, the prevalence of resistance rates should be taken into consideration in selecting quinolone-containing treatments as a rescue therapy.

LEVOFLOXACIN-CONTAINING THERAPIES

Levofloxacin, one of the third-generation fluoroquinolones, is available worldwide.There is abundant evidence of levofloxacin-containing rescue regimens (Table 1)[36-64].Wonget al[36]showed the efficacy of levofloxacin-rifabutin-rabeprazole triple therapy as a rescue therapy in 2003. However, in this study, one patient developed drugrelated neutropenia and thrombocytopenia, thus they concluded that rifabutin should be reserved only for resistant cases or even as a third-line therapy[36]. In addition,Zulloet al[37]and Nistaet al[38]reported the efficacy of 10-d levofloxacin-amoxicillinrabeprazole triple therapy as a third- and second-line rescue therapy, respectively,and the eradication rates seem to be sufficient (88.2% and 94.3%, respectively)[37,38]. On the other hand, Perriet al[39]and Watanabeet al[40]revealed that the efficacy of 7-d levofloxacin-amoxicillin-rabeprazole triple therapy as a second-line regimen is insufficient (66.1% and 69.7%, respectively)[39,40]. Matsumotoet al[42]showed that 7-d metronidazole-amoxicillin-lansoprazole triple therapy is significantly more effective than 7-d levofloxacin-amoxicillin-lansoprazole triple therapy as a second-line therapy in a prospective randomized trial in Japan (100.0%vs72.4%, respectively)[42]. As a result, 7-d metronidazole-amoxicillin-lansoprazole triple therapy was confirmed as a second-line treatment in Japan[14]. The remarkable efficacy of 7-d metronidazoleamoxicillin-lansoprazole triple therapy is definitely due to the low rate of metronidazole-resistant strains in Japan, which seems to be an exceptional situation[65].Moreover, Murakamiet al[58]revealed that 7-d sitafloxacin-amoxicillin-lansoprazole triple therapy is significantly more effective than 7-d levofloxacin-amoxicillinlansoprazole triple therapy as a third-line therapy in a prospective randomized trial in Japan (70.0%vs43.1%, respectively). At present, levofloxacin containing triple therapy is no longer used in Japan[14].

Di Caroet al[47]conducted a randomized study to determine dosage and length of levofloxacin-containing regimens as a second-line rescue treatment. In this study,patients were randomized into 4 groups to receive 7-d or 10-d levofloxacin 500 mg,amoxicillin 2000 mg and esomeprazole 40 mg per day or 7-d or 10-d levofloxacin 1000 mg, amoxicillin 2000 mg and esomeprazole 40 mg per day. Interestingly, based upon duration of treatment, eradication rates in the 10-d groups were significantly higher than those in the 7-d groups (87.5%vs67.5 %, respectively); however, dosage of levofloxacin did not affect the eradication rates (77.5%vs77.5%, respectively)[47].Similarly, Taiet al[57]showed that the eradication rate of 14-d levofloxacin-amoxicillinlansoprazole triple therapy was higher than that of 10-d levofloxacin-amoxicillinlansoprazole triple therapy (92.5%vs75.6%, respectively). A meta-analysis showed that the eradication rates of 10-d levofloxacin-containing regimens were significantly higher than those of 7-d levofloxacin-containing regimens (81.0%vs73.0%,respectively)[66]. One other meta-analysis also showed 14-d levofloxacin-containing regimens seemed to be more effective compared to 7-d levofloxacin-containing regimens (83.4%vs74.6%, respectively)[67]. These data suggested the dose and duration of levofloxacin-containing regimens of 500 mg per day for 10-14 d should be sufficient.

Figure 1 Primary resistance of Helicobacter pylori to levofloxacin in different countries.

From 2013, levofloxacin and bismuth-containing regimens were reported as rescue treatments[55]. Gisbertet al[59]achieved 91.1% of eradication with 14-d levofloxacinamoxicillin-esomeprazole-bismuth regimen as a second-line therapy. Hsuet al[64]showed 10-d levofloxacin-tetracycline-esomeprazole-bismuth regimen was more effective than levofloxacin-amoxicillin-esomeprazole triple regimen as a second-line therapy (97.8%vs68.6%, respectively). On the other hand, Caoet al[60]revealed that 14-d levofloxacin-amoxicillin-lansoprazole-bismuth regimen was less effective compared to 14-d classical metronidazole-tetracycline-lansoprazole-bismuth quadruple therapy in areas of high quinolones resistance such as China (85.4%vs90.6%, respectively).

Some reports showed the efficacies of modified sequential therapy containing levofloxacin[49,55,62]. Liouet al[62]revealed modified sequential therapy containing levofloxacin was more effective than 10-d levofloxacin-amoxicillin-lansoprazole triple regimen in the second-Line treatment (86.3%vs78.8%, respectively). On the other hand, Calhanet al[55]showed that modified sequential therapy containing levofloxacin was less effective than 10-d levofloxacin-tetracyclin-pantoprazole-bismuth quadruple regimen (85.7%vs93.1%, respectively).

Eradication rates of levofloxacin-containing regimens against levofloxacin-resistant strains orgyrAmutation-positive strains were reported to be 33.3% to 41.7%[20,45], while those of sitafloxacin-containing regimens were 68.4% to 74.4%[8,9,68]. Moreover, 7-d or 10-d sitafloxacin-containing regimens, achieved almost perfect eradication ofgyrAmutation-negative strains, whereas the eradication rate of a 7-d levofloxacincontaining triple regimen was only 82.7%[9,20].

Regarding adverse effects, levofloxacin-containing triple therapies are more tolerable compared to bismuth-containing quadruple therapy[66]. 10- and 14-d levofloxacin-containing triple therapies are equally safe compared to 7-d levofloxacincontaining triple therapy[57,66].

From these data, when levofloxacin-containing regimens are used as a rescue therapy, a drug sensitivity test or an analysis ofgyrAmutation should be performed before treatment. In areas of high quinolones resistance, classical bismuth-containing quadruple therapy or fourth-generation fluoroquinolone, such as sitafloxacin, -containing regimen seems to be better choices. Modified sequential therapy containing levofloxacin or 10-d levofloxacin-tetracyclin-PPI-bismuth quadruple regimen could be an option as a third-line regimen.

Table 1 Levofloxacin-containing therapies

MOXIFLOXACIN-CONTAINING THERAPIES

Moxifloxacin, one of the third-generation fluoroquinolones, is available worldwide.Di Caroet al[69]initially showed the efficacy of moxifloxacin-based therapies as a firstline therapy at first in 2002. Cheonet al[70]reported moxifloxacin-amoxicillinesomeprazole triple therapy achieved 83.8% successful eradication, and significant superiority to bismuth- containing regimen in Korea. The reports of moxifloxacincontaining therapies were shown in Table 2. Most of the reports were published from South Korea. Interestingly, 7-d moxifloxacin-amoxicillin-PPI triple therapy achieved over 78% in PP before 2011[71-74]; from 2014 the eradication rates gradually decreased and hovered around 60%[75-79]. On the other hand, 14-d moxifloxacin-amoxicillin-PPI triple therapy is more effective than 7-d regimen, and maintains the efficacy over 80%in PP. These data suggested that 7-d moxifloxacin-amoxicillin-PPI triple therapy should not be used as a second-line regimen in Korea any longer. It is believed that the diminished effectiveness of 7-d moxifloxacin-amoxicillin-PPI triple therapy was attributed to increasing antimicrobial resistance ofH. pylorito quinolones, especially in Korea[27,80]. Maru?i?et al[81]showed that 14-d bismuth-based quadruple therapy modified with moxifloxacin achieved 88.0 % of eradication in Croatia as a second-line treatment, thus this regimen might be useful in regions of low metronidazole resistance.

Few reports are available on whether levofloxacin- or moxifloxacin-containing therapy is a better rescue therapy. As a first-line treatment, Rakiciet al[82]performed randomized trial between levofloxacin-amoxicillin-lansoprazole triple therapy and moxifloxacin-amoxicillin-lansoprazole triple therapy, and there was no significant difference (92.0%vs91.8%, respectively). The side effects observed in the two groups were similar.

In conclusion, levofloxacin- or moxifloxacin-containing therapies seem to be equally effective as second-line treatments; thus, either regimens can be used at present. In regions of high quinolones resistance, 14-d moxifloxacin-amoxicillin-PPI triple therapy is better choice than 7-d regimen. Few data are available on 10-d regimen, thus future research is needed to confirm its efficacy as a second-line therapy.

SITAFLOXACIN-CONTAINING THERAPIES

Sitafloxacin, one of the fourth-generation fluoroquinolones, is only available in Japan and Thailand. The reports of sitafloxacin-containing therapies were shown in Table 3.Sánchezet al[83]initially showed that sitafloxacin was the most active fluoroquinolone compared with ciprofloxacin and moxifloxacinin vitro. Moreover, we reported that sitafloxacin exhibited the most potent activity againstgyrAmutation-positive strains compared with gatifloxacin and garenoxacin, two other fourth-generation fluoroquinolones[84]. Murakamiet al[85]also showed that sitafloxacin had a strong activity compared with garenoxacin and levofloxacinin vitro. Based on thesein vitrodata, we revealed that sitafloxacin-amoxicillin-rabeprazole triple therapy achieved 83.6% success in eradicatingH. pylorias a third-line rescue treatment[8]. Moreover,even among patients withgyrAmutation-positiveH. pylori, the eradication rates reached to be 74.4%. Multi-center randomized controlled study showed that sitafloxacin-amoxicillin-lansoprazole triple therapy achieved 70.0% of successful eradication as a third-line rescue treatment, whereas the eradication rates of levofloxacin-amoxicillin-lansoprazole triple therapy and high dose amoxicillinlansoprazole dual therapy were 43.1% and 54.3%, respectively[58]. We examined randomized controlled study to assess the efficacy with extension of the duration of regimens from 7 to 10 d and the efficacy of sitafloxacin-metronidazole-esomeprazole triple therapy as a third-line rescue treatment[9]. However, there was no significant difference in the eradication rates between 10-d sitafloxacin-amoxicillin-esomeprazole triple therapy and 10-d sitafloxacin-metronidazole-esomeprazole triple therapy(82.0%vs76.4%,P= 0.50)[9]. The 10-d regimens also could not improve eradication rates when compared with the 7-d sitafloxacin-containing regimen[9]. Furutaet al[86]compared sitafloxacin-amoxicillin-rabeprazole for 7 or 14 d or sitafloxacinmetronidazole-rabeprazole for 7 or 14 d; however, there were no significant difference between them. Recently, a randomized trial showed that 7-d sitafloxacin-amoxicillinvonoprazan triple therapy is more effective than 7-d sitafloxacin-amoxicillinesomeprazole triple therapy as a third-line regimen (83.3%vs57.1%,P= 0.04)[87].Vonoprazan, a first-in-class potassium-competitive acid blocker, exhibits more rapid,strong, and continuous gastric acid suppression was compared with conventional PPIs[10]. Vonoprazan-containing regimens showed more efficacy than PPI-containing regimens in first- and second-line treatments[10,11]. Recently, we revealed that changes in the rate of resistance to sitafloxacin were not observed from 2009 to 2015[68].

Regarding adverse events to sitafloxacin-containing regimens, severe side effectsare rarely reported. Mild and transient adverse effects, such as diarrhea and soft stool,were reported by 24%-80% of patients who received treatments[68,86,87].

Table 2 Moxifloxacin-containing therapies

These data suggested that 7-d sitafloxacin-amoxicillin-vonoprazan triple therapy is the best choice for third-line treatment at the current moment. However, the efficacy of 7-d sitafloxacin-amoxicillin-vonoprazan triple therapy togyrAmutation-positiveH.pylorishould be evaluated in the future.

ANTIBIOTIC RESISTANCE INFLUENCES DUE TO ERADICATION FAILURE WITH QUINOLONE-CONTAINING RESCUE THERAPIES

Wueppenhorstet al[88]showed that the levofloxacin/ciprofloxacin resistance occurred significantly more often in patients who had received quinolones-containing regimen when compared with patients who had not (44.5%vs23.1%). We found that 20.8% of strains obtained double mutations ingyrAafter eradication failure with stafloxacincontaining third-line treatment, which exhibited seven-fold increased MICs of sitafloxacin compared with pre-treatment. On the other hand, the MICs of sitafloxacin did not increase, when the location of thegyrAmutations did not change after treatment. Double mutations ingyrAalso cause higher resistance to other fluoroquinolones[22]. If strains obtain new mutation ingyrA, quinolone-containing regimen will be less effective. Therefore, we recommend a more powerful regimen to be used,e.g., sitafloxacin-containing or extension of duration, and stronger inhibition of gastric acid secretion, when quinolone-containing regimen is used as a rescue treatment.

CONCLUSION

Quinolone-containing regimen is effective as a rescue treatment. The drug susceptibility test to quinolones and the identification ofgyrAmutation arerecommended before using quinolone-containing regimen. In using levofloxacincontaining regimen, 10- or 14-d regimen or bismuth containing regimen are recommended and should be restricted to regions of low levofloxacin resistance.Seven-day sitafloxacin-amoxicillin-vonoprazan triple therapy is the best choice for third-line treatment at the current moment.

Table 3 Sitafloxacin-containing therapies