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Fosfomycin Trometamol Compared With an Alternative Active Antibiotic as Step-down Therapy for the Treatment of Acute Pyelonephritis Due to Escherichia Coli in Elderly Women : a Randomized, Multicenter, Non-inferiority Trial (FOSFOLD)

5 november 2026 uppdaterad av: Assistance Publique - Hôpitaux de Paris

Fosfomycine trométamol comparé à un Autre Traitement Antibiotique Actif en Relais Pour le Traitement Des pyélonéphrites aiguës à Escherichia Coli Chez Les Femmes âgées : Essai randomisé, Multicentrique de Non infériorité

Acute pyelonephritis (APN) is among the most common bacterial infections in older women. Oral step-down antibiotic therapy may potentially be associated with toxicity, particularly with fluoroquinolones or trimethoprim-sulfamethoxazole, espcially in geriatric patients. The emergence of resistant strains reduces the choice of oral step-down treatment, thereby increasing the risk of nosocomial complications related to intravenous access and prolonged hospitalization.

Fosfomycin trometamol (FT) has broad activity against Enterobacterales, including resistant strains. It has an excellent safety profile and moderate ecological impact, and has been used for several years to treat cystitis. Recent studies have demonstrated its efficacy as an oral step-down therapy for the treatment of E.coli APN in younger women. Its efficacy in a geriatric population remains to be demonstrated.

The primary objective is to demonstrate the non-inferiority, in terms of clinical cure, of FT compared with an alternative active antibiotic as step-down therapy for E. coli APN in older women.

FOSFOLD is a national, multicenter, randomised, comparative, phase 3, non-inferiority trial (1:1), open-label with two parallel treatment groups. After 3 or 4 days of appropriate empirical antibiotic therapy, women aged 75 or over with E.coli APN will be randomised to receive either 3g of FT once daily or an alternative antibiotic treatment in accordance with current french guidelines, for a total of 10 days.

The primary endpoint is clinical cure at Day 17, i.e. 10 days after completion of antibiotic therapy.

If non-inferiority of FT is confirmed, it could provide a new therapeutic approach for oral step-down therapy in the older patients with APN. Its favorable tolerability profile could help prevent common geriatric complications, such as delirium, falls and malnutrition. Ultimately, it could help prevent some of the iatrogenic functional decline associated with hospitalisation.

Studieöversikt

Studietyp

Interventionell

Inskrivning (Beräknad)

312

Fas

  • Fas 3

Kontakter och platser

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Studiekontakt

Studera Kontakt Backup

Deltagandekriterier

Forskare letar efter personer som passar en viss beskrivning, så kallade behörighetskriterier. Några exempel på dessa kriterier är en persons allmänna hälsotillstånd eller tidigare behandlingar.

Urvalskriterier

Åldrar som är berättigade till studier

75 år och äldre (Äldre vuxen)

Tar emot friska volontärer

Nej

Kön som är behöriga för studier

Kvinna

Beskrivning

Inclusion Criteria:

  1. Female.
  2. Age ≥ 75 years.
  3. Body temperature ≥ 38°C on at least once during the 72 hours preceding diagnosis.
  4. At least one new symptom among the following : urinary urgency, dysuria, increased urinary frequency, gross hematuria, burning on urination, spontaneous of provoked flank or suprapubic pain or urinary incontinence.
  5. Positive urine culture collected before initiation of antibiotic therapy defined as : ≥ 10,000 leukocytes/mL and monomicrobial culture with Escherichia coli ≥ 103 CFU/mL and susceptibility to FT,the empirical antibiotic,and at least one alternative antibiotic (active and not contraindicated), administered either orally (fluoroquinolone, amoxicillin, amoxicillin-clavulanic acid, or trimethoprim-sulfamethoxazole or, in the absence of an oral alternative, intravenously.
  6. Ability to reveive oral medication
  7. Favorable clinical course after 3 or 4 days of effective empirical antibiotic therapy, defined as resolution of fever (temperature < 38°C) and regression or reduction in the intensity and/or frequency of the clinical sign(s) present at the time of APN diagnosis, without the occurrence of any new symptoms.

Exclusion Criteria:

  1. Presence of an infectious focus other than the urinary tract.
  2. Severe infection and/or initial infectious complications, including septic shock, requirement for an emergency upper urinary tract intervention, or renal abscess.
  3. Indwelling urinary catheter, including bladder, ureteral, or nephrostomy catheters.
  4. Inability to take oral medication.
  5. Immunosuppression, including sold-organ transplant, ongoing immunosuppressive therapy, ongoing chemotherapy.
  6. Hypersensitivity to fosfomycin trometamol or to any of the excipients of the study medication
  7. End-stage chronic kidney disease with an estimated glomerular filtration rate (eGFR) < 15 mL/min/1.73 m2.
  8. Lack of health insurance coverage.
  9. Patient under legal protection or guardianship.
  10. Absence of written informed consent from the patient or, if the patient is unable to provide consent, absence of agreement from the designated trusted person or a close relative.
  11. Participation in another interventional clinical research protocole

Studieplan

Det här avsnittet ger detaljer om studieplanen, inklusive hur studien är utformad och vad studien mäter.

Hur är studien utformad?

Designdetaljer

  • Primärt syfte: Behandling
  • Tilldelning: Randomiserad
  • Interventionsmodell: Parallellt uppdrag
  • Maskning: Ingen (Open Label)

Vapen och interventioner

Deltagargrupp / Arm
Intervention / Behandling
Experimentell: Fosfomycin-trometamol (FT)

One sachet (3g), once daily, orally for 6 or 7 days, following 4 or 3 days, respectivelly of effective antibiotic therapy, for a total of 10 days of effective antibiotic treatment.

Aktiv komparator: Alternative antibiotic treatment

Treatment will be selected at the investigator's discretion, in accordance with the 2017 recommandations of the French Society for Infectious Diseases (SPILF) and the 2025 French National Authority for Health (HAS) guidelines. Therapy will be administrated for 6 or 7 days (Day 1 - Day 6/7), following 4 or 3 days, respectively of effective antibiotic therapy. The total duration of effective antibiotic therapy will be 10 days. Injection antibiotic therapy will be offered in the absence of an active oral antibiotic option.

Vad mäter studien?

Primära resultatmått

Resultatmått
Åtgärdsbeskrivning
Tidsram
Clinical resolution
Tidsram: Day 17

Clinical cure defined as :

  • Body temperature < 38 °C and resolution of all urinary symptoms present at the time of the APN diagnosis, with no occurrence of new clinical signs (urinary urgency, dysuria, increased urinary frequency, gross hematuria, painful/burningurination, flank pain [spontaneous or provoked], suprapubic pain, or urinary incontinence) between treatment discontinuation and assessment of the primary endpoint at Day 17, except for a temperature ≥ 38°C unrelated to a urinary tract condition
  • No resumption of antibiotic therapy active against the causative pathogen responsible for the APN following completion of the antibiotic treatment course
Day 17

Sekundära resultatmått

Resultatmått
Åtgärdsbeskrivning
Tidsram
Occurence of antibiotic-related adverse events
Tidsram: Up to 37 days

Occurrence, nature, and severity of antibiotic-related adverse events, assessed using the National Cancer Institute Common Terminology Criteria for Adverse Events (CTCAE) scale.

Up to 37 days
Occurence of geriatric complications
Tidsram: Up to 37 days
  • Occurrence of delirium, defined according the Confusion Assessment Method (CAM)
  • Fall(s) (one or more episodes)
  • Weight loss, assessed as the percentage change between admission body weight and discharge body weight or Day 17 weight if the patient remains hospitalized
  • Occurrence of pressure ulcers, staged according to the National Pressure Ulcer Advisory Panel (NPUAP) pressure ulcer staging classification (HAS Guidelines, Prevention and Treatment of Pressure Ulcers in Adults and Older Persons, 2001)
Up to 37 days
Functional autonomy
Tidsram: Up to 37 days

According to the Activities of Daily Living (ADL) scale: score ranges from 0 (complete dependence) to 6 (complete independence), with higher scores indicating greater independence in basic daily activities such as bathing, dressing, toileting, transferring and eating.

Up to 37 days
Incidence of Infectious and urological complications
Tidsram: Up to day 7
  • Renal abscess (yes/no)
  • Need for urinary drainage
  • Transfer to an continuous care unit or intensive care unit due to the infection At the end of antibiotic treatment (Day 7)
Up to day 7
Cumulative incidence of recurrent febrile or non-febrile urinary tract infectious (UTIs) (relapse or reinfection)
Tidsram: From Day 17 to Day 37
  • Cystitis : recurrence of urinary symptoms in the absence of fever, associated with a positive urine culture.
  • Acute pyelonephritis :; recurrence of urinary symptoms with fever and a positive urine culture.
  • Reinfection : new infection caused by a microorganism different from that isolated during the initial episode.
  • Relapse : recurrence of infection due to the same microorganism as that isolated during the initial episode.
From Day 17 to Day 37
Rate of hospitalization or rehospitalization following treatment for APN
Tidsram: Up to day 37
Up to day 37
Length of hospital stay following randomization
Tidsram: Up to day 37
Up to day 37
All-cause mortality
Tidsram: Up to day 37
Up to day 37
Rate of rectal colonization with antibiotic-resistant Enterobacterales
Tidsram: Up to day 37

fluoroquinolones, trimethoprim-sulfamethoxazole, fosfomycin, and third-generation cephalosporins

Up to day 37

Samarbetspartners och utredare

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Studieavstämningsdatum

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Studera stora datum

Studiestart (Beräknad)

1 december 2026

Primärt slutförande (Beräknad)

17 januari 2030

Avslutad studie (Beräknad)

15 februari 2030

Studieregistreringsdatum

Först inskickad

29 oktober 2026

Först inskickad som uppfyllde QC-kriterierna

5 november 2026

Första postat (Faktisk)

10 november 2026

Uppdateringar av studier

Senaste uppdatering publicerad (Faktisk)

10 november 2026

Senaste inskickade uppdateringen som uppfyllde QC-kriterierna

5 november 2026

Senast verifierad

1 oktober 2026

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