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- Patients and methods
Cryptosporidium species are protozoan parasites with worldwide distribution. After being ingested by humans, the organism infects the intestinal tract causing a disease known as cryptosporidiosis. Cryptosporidium gained notoriety in the USA following a large waterborne outbreak of cryptosporidiosis in Milwaukee, Wisconsin in 1993. Before the advent of highly active antiretroviral therapy in the last half of the 1990s, it was also recognized as an important cause of morbidity and mortality in subjects with acquired immune deficiency syndrome (AIDS).1–3
In immunocompetent subjects, cryptosporidiosis is characterized by watery or mucoid diarrhoea and abdominal pain with spontaneous recovery following several days or weeks of symptoms. Cryptosporidiosis is more severe in immunocompromized subjects (e.g. because of young or old age, malnutrition, cancer chemotherapy, transplant patients, etc.). In subjects with immune deficiencies (e.g. AIDS or common variable immunodeficiency), cryptosporidiosis constitutes a serious threat leading to chronic or fulminant disease, wasting and death.1, 2 While improved antiretroviral regimens have significantly reduced the prevalence of AIDS and AIDS-related opportunistic infections, cryptosporidiosis remains among the most common causes of diarrhoea in patients with AIDS.1, 4
Nitazoxanide, the first of a new class of drugs called the thiazolides, is effective against Cryptosporidium parvum in cell culture and in several animal models of intestinal and biliary cryptosporidiosis.5–9 Randomized double-blind placebo-controlled clinical trials have shown that a short course of treatment reduces the duration of diarrhoea and oocyst shedding in adults (500 mg b.d. for 3 days) and children (8 mg/kg b.d. for 3 days) without immune deficiencies.10, 11 The same course of treatment also reduced the mortality among the malnourished young children hospitalized with cryptosporidiosis.12
In subjects with AIDS-related cryptosporidiosis, nitazoxanide has been used at higher doses and for longer durations. A double-blind, placebo-controlled study showed that 1000 mg administered twice daily for 14 days is effective in resolving the symptoms and eliminating the oocysts from the stool in AIDS patients with CD4 counts <50 cells/mm3, but not in patients with CD4 counts below 50 cells/mm3.13 Other attempts to conduct randomized placebo-controlled trials in patients with AIDS-related cryptosporidiosis have been unsuccessful in patient recruitment because of (i) the very serious nature of the disease in these patients and (ii) a marked decline in prevalence of the disease after the advent of highly active antiretroviral therapy.
Between 1995 and 2002, nitazoxanide was made available to patients with AIDS-related cryptosporidiosis in the USA pursuant to a compassionate use study protocol registered with the United States Food and Drug Administration. This study became the largest study ever conducted in treating the AIDS-related cryptosporidiosis. While the study was not a randomized-controlled clinical trial, it did provide a large amount of data related to the use of nitazoxanide in treating this very serious disease. This report summarizes the findings of the compassionate use program.
Patients and methods
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- Patients and methods
In early 1995, soon after the first report of the in vitro efficacy of nitazoxanide against C. parvum, a compassionate use program was established to provide access to the drug to patients who were unable to participate in well-controlled clinical trials. Initially, adult patients received a 500-mg oral dose twice daily, and children ages 3–14 years received an 8 mg/kg oral dose twice daily for a maximum of 30 days. After gaining the additional experience with the 500-mg dose, the protocol was subsequently modified to allow for administration of doses up to 1500 mg b.d. or 23 mg/kg b.d. in children, and limitations on the duration of treatment were removed.
Patients eligible for inclusion in the study were at least 3 years of age, HIV-positive and had at least 2 weeks of diarrhoea (4 weeks if CD4 count >200/mm3) and a positive stool examination for C. parvum oocysts by using an available methodology. Pregnant females, females of child-bearing age not using birth control, patients with other causes of diarrhoea identified by stool ova and parasite examination, patients with Mycobacterium avium infection or intestinal Kaposi's sarcoma, patients with a history of cytomegalovirus (unless 28 days of therapy with ganciclovir or foscarnet had been completed) and patients receiving therapy with other potential anticryptosporidial therapies (paromomycin, spiramycin, azithromycin or clarithromycin) were excluded from the enrollment in the study.
Before enrolling in the study, patients were evaluated for inclusion/exclusion criteria, medical history and stool examination to establish the diagnosis of cryptosporidiosis. Procedures at baseline included the medical history (including concomitant medications), physical examination, collection of stool for ova and parasite examination (including Cryptosporidium), collection of serum for laboratory safety tests, instructions for completing a patient diary of symptoms and medication compliance, evaluation of symptoms by using an associated symptoms questionnaire. Each of these procedures plus a review of adverse events were repeated at weeks 1, 2, 4 and monthly thereafter while the patient remained on treatment. Because of the life-threatening nature of AIDS-related cryptosporidiosis, patients were allowed to continue treatment as long as they and their physicians believed that there were benefits. A final evaluation was conducted 2 weeks following the end of the treatment.
At baseline and at each visit during the treatment, patients competed a symptoms questionnaire indicating the severity and frequency of nausea, vomiting, abdominal pain, urgency, incontinence, and night-time bowel movements during the week immediately preceding the visit. The severity of symptoms was recorded on a scale of 1–4, with 1 representing no impact on daily activity, 2 mild impact, 3 moderate impact and 4 marked impact. Frequency was simply the average number of episodes per day. A symptom index (frequency × impact score) was calculated for each symptom. The patients have also used a ranking system to describe the change in their global assessment of symptoms of cryptosporidiosis and their global assessment of overall health as baseline. The patients’ global assessments were ranked on a scale from 1 to 7, with 7 representing marked improvement, 6 moderate improvement, 5 slight improvement, 4 no change, 3 slight worsening, 2 moderate worsening and 1 marked worsening.
Adverse events were recorded on case report forms and graded on a 4-point scale, as mild, moderate, severe or life threatening. The study medication was discontinued in any subject experiencing a grade 4 toxicity. Treatment compliance was assessed using the patient diaries and counting tablets returned at each study visit. In order to ensure the appropriate collection of data, the study medication was supplied to study sites only upon receipt of completed case report forms. Telephone contact was maintained with investigators to obtain the missing data and to confirm that no adverse events had gone unreported.
Efficacy data were analysed on an intention-to-treat basis for all subjects who received study medication. Efficacy endpoints included clinical response, changes in global assessment of symptoms and global assessment of overall health over time, and parasitological response. Clinical response was defined as a sustained improvement in the patient's global assessment of gastrointestinal symptoms while on treatment accompanied by improvements in stool frequency and consistency and severity and frequency of nausea, vomiting, abdominal pain, urgency, incontinence and night-time bowel movements. Patients not satisfying the definition of clinical response were considered non-responders. Parasitological response was determined based on the last parasitological examination result for each patient. Patients stool-negative for Cryptosporidium oocysts were considered parasitological responders. All others were considered parasitological failures. Response data were summarized. Analyses were conducted to evaluate the correlation of clinical and parasitological responses using chi-squared or Fisher's exact tests. Exploratory analyses were carried out to identify the important co-variates that may have affected the treatment response.
The compassionate use program was carried out under an Investigational New Drug Application filed with the United States Food and Drug Administration. The protocol and protocol amendments were approved by the Institutional Review Board for each participating physician, and each patient provided written informed consent prior to participation in the study.
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Three hundred and sixty-five patients were enrolled at 165 participating study centres. Eight patients were excluded from the efficacy analyses because they were not HIV-infected. Demographic- and disease-related characteristics of the 357 patients included in the efficacy analysis are summarized in Table 1. The duration of the treatment for the 365 patients enrolled in the study ranged from 1 day to 4 years (median 62 days). Duration of treatment data is summarized by age, gender and dosage regimens in Table 2.
Table 1. Demographic and disease-related characteristics at baseline
| ||Adults (20–65 years)||Adolescents (12–19 years)||Children (3–11 years)|
| Mean ± SD||39 ± 7||14 ± 2||7 ± 2|
| Mean ± SD||66 ± 11||29 ± 5||18 ± 4|
|CD4 count (cells/mm3)|
| Mean ± SD||49 ± 75||50 ± 46||99 ± 130|
| Median (range)||23 (0–668)||50 (1–123)||50 (2–412)|
|Weeks since diagnosis of cryptosporidiosis|
| Mean ± SD||25 ± 32||32 ± 20||18 ± 19|
|Liquid stools/day|| || || |
| Mean ± SD||8 ± 8||7 ± 5||5 ± 3|
|Number of antidiarrhoeals daily|
| Mean ± SD||4 ± 3||3 ± 1||–|
Table 2. Summary of the duration of treatment
| ||All pts||<1 week||1–2 weeks||2–4 weeks||1–2 months||2–3 months||3–6 months||>6 months|
| Female||23|| 1|| 2|| 5|| 6|| 1|| 1|| 7|
| ≤14||16|| –|| 1|| 2|| 4|| 2|| 2|| 5|
| 15–19||3|| –|| –|| –|| –|| 1|| –|| 2|
| 20–29||17|| 3|| 2|| 2|| 2|| 2|| 1|| 5|
| 30–39||172|| 7||10||36||34||24||37||24|
| 40–49||129|| 4|| 6||26||28||24||22||19|
| 50–59||25|| –|| 2|| 4|| 4|| 3|| 7|| 5|
| ≥60||3|| 1|| –|| –|| 1|| –|| 1|| –|
|≤14 years (mg/kg/day)|
| 15||4|| –|| 1|| 1|| –|| 1|| –|| 1|
| 15–30||3|| –|| –|| –|| 1|| –|| 1|| 1|
| 15–80||1|| –|| –|| 1|| –|| –|| –|| –|
| 30||4|| –|| –|| –|| 2|| 1|| –|| 1|
| 30–45||2|| –|| –|| –|| 1|| –|| 1|| –|
| 30–60||1|| –|| –|| –|| –|| –|| –|| 1|
| 45||1|| –|| –|| –|| –|| –|| –|| 1|
|>14 years (mg/d)|
| 1000||165|| 6|| 8||41||39||29||25||17|
| 1000–2000||27|| –|| –|| 1|| 5|| 1|| 6||14|
| 1000–3000||10|| –|| –|| –|| –|| –|| 4|| 6|
| 2000||116|| 9||11||25||20||17||23||11|
| 2000–3000||29|| –|| –|| 1|| 4|| 7||10|| 7|
| 3000||2|| –|| 1|| –|| 1|| –|| –|| –|
Among the 357 patients with AIDS-related cryptosporidiosis, 324 submitted the data allowing for evaluation of clinical response. Two hundred and nine patients (59% of all patients enrolled, 65% of evaluable patients) achieved a sustained clinical response. The clinical response of these patients is evidenced by the improvement of their assessment of gastrointestinal symptoms and overall health during the first 12 weeks of treatment (Figure 1). Mean frequency of liquid stools and total stools declined rapidly from the baseline to week 1 in this group and continued to improve thereafter, although less rapidly through week 12 (Figure 2). Other symptoms such as nausea and vomiting, abdominal pain, urgency, incontinence and night-time bowel movements followed a similar pattern (Figure 3). The mean time to clinical response was 2 weeks.
Figure 1. Mean global assessment scores by visit for patients with a sustained clinical response. 1 = markedly worse, 2 = moderately worse, 3 = slightly worse, 4 = no change, 5 = slightly improved, 6 = moderately improved, 7 = markedly improved. Number of patients reporting data at each time point = 205 at baseline, 142 at week 1, 176 at week 2, 163 at week 4, 103 at week 8, 64 at week 12.
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Figure 2. Mean daily stool frequency by visit for patients with a sustained clinical response. Number of patients reporting the data at each time point = 205 at baseline, 142 at week 1, 176 at week 2, 163 at week 4, 103 at week 8, 64 at week 12.
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Figure 3. Mean symptom index values by visit for patients with a sustained clinical response. Symptom index = daily frequency of symptoms during the week prior to the visit multiplied by the impact rating (1 = no impact, 2 = mild impact, 3 = moderate impact, 4 = marked impact). Number of patients reporting the data at each time point = 205 at baseline, 142 at week 1, 176 at week 2, 163 at week 4, 103 at week 8, 64 at week 12.
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Two hundred and two patients submitted at least one stool sample for parasitological examination after the treatment was initiated. One hundred and sixteen patients (33% of all patients enrolled, 57% of evaluable patients) had Cryptosporidium-negative stool at the last examination before completing the study while 86 patients had Cryptosporidium-positive stool. The mean time to first negative stool examination was 7 weeks. More than 75% of patients who achieved parasitological response did so by week 8. Ninety-six of the 115 parasitological responders (84%) experienced a sustained clinical response compared with only 37 of the 85 (44%) parasitological failures (P < 0.0001). Each of the patients who resolved their symptoms of cryptosporidiosis and cleared oocysts from their stool sustained their responses at the final visit 2 weeks after the discontinuation of treatment. Twenty clinical responders discontinued the treatment prior to clearing oocysts from their stools, and 18 of these patients experienced the recurring symptoms and re-initiated treatment.
Analyses were also conducted to determine the effect of CD4 count on clinical response and last parasitology result for the 343 adults with AIDS and cryptosporidiosis. Among the evaluable patients, relationships between CD4 counts and clinical response and CD4 count and last parasitology result were apparent (P = 0.072 and P = 0.0051, respectively), and those with higher CD4 counts were more likely to achieve both the sustained clinical response and negative parasitology results.
Patients who did not achieve a clinical response were nearly twice as likely as responders to discontinue the study because of AIDS-related illness or death, die during the course of the study because of a complication of AIDS, and/or have an AIDS-related serious adverse event on a given treatment. No significant differences for clinical or parasitological response rates were found between the 500- and 1000-mg dosing groups, however. Nor were there significant differences in response rates found for patients who were on combinations of antiretrovirals when compared with those who were not.
Two hundred and three patients reported a total of 482 adverse events during the course of the study. Three hundred and forty-nine adverse events (72%) were complications of the patients’ underlying disease and were unrelated to the use of nitazoxanide. Eighty-three patients (23%) died during the study or within 12 weeks following the end of treatment. None of the deaths or other serious adverse events (life-threatening or requiring hospitalization) was reported to be related to the use of nitazoxanide. Twenty-seven non-serious adverse events were considered possibly related to the use of the study drug. Twenty of these events were associated with the digestive tract (nausea, vomiting, diarrhoea, abdominal pain and dyspepsia). Other events possibly related to treatment were allergic reaction (n = 2), rash (n = 1), yellowish discolouration of the sclera (n = 2), and discolouration of urine (n = 2). Each of these events was transient in nature resolving on treatment or upon the discontinuation of treatment.
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Cryptosporidiosis in immunodeficient patients, and particularly in subjects with AIDS, is a serious, life-threatening disease. The disease is far less common as the introduction of highly active antiretroviral therapies; nevertheless, there remains a need for an effective treatment.1, 2, 4
Three double-blind placebo-controlled clinical trials have shown that nitazoxanide is effective in treating the cryptosporidiosis in non-immunodeficient adults and children, and it is the first drug approved in the USA for treating this disease (Alinia; Romark Laboratories, Tampa, FL, USA).10–12 In a study involving the malnourished young children hospitalized with cryptosporidiosis, nitazoxanide reduced the mortality compared with a placebo.12 A study conducted in patients with AIDS-related cryptosporidiosis in Mexico before the era of highly active antiretroviral therapy showed that a 14-day course of nitazoxanide administered 1000 mg b.d. eradicated Cryptosporidium oocysts from the stools of 90% of patients with CD4 counts higher than 50 cells/mm3 compared with 71% in those treated with 500 b.d., the response rates for both dose groups being superior to that of the placebo. No significant difference was observed, however, in patients with CD4 counts below 50 cells/mm3.13
Another double-blind placebo-controlled trial in Thailand studied the safety and effectiveness of nitazoxanide administered 1000 mg b.d. for 8 weeks in patients with AIDS-related cryptosporidiosis, CD4 counts below 50 cells/mm3 and without access to antiretroviral therapy. This study was terminated early because of difficulty in recruiting the patients. Intention-to-treat analysis of the 41 patients enrolled in the study showed an end-of-treatment clinical response occurred in seven of 22 nitazoxanide-treated patients (32%) vs. one of 19 (5%) in the placebo group (P = 0.049). Cryptosporidium oocysts were eradicated from the stools of only two of these nitazoxanide-treated responders compared with none of the placebo patients. This placebo-controlled study did not identify any significant differences in adverse events reported for nitazoxanide-treated patients compared with the placebo-treated patients in this very ill population.
The main limitation of the compassionate use study is that it is not a randomized-controlled study. Cryptosporidial disease can be variable and self-limiting in some patients, and therefore, uncontrolled data can be difficult to interpret. Nevertheless, the results observed in this study and in this population are impressive. Sixty-six per cent of evaluable patients achieved a sustained clinical response to nitazoxanide therapy. Most patients experiencing a clinical response did so within the first 2 weeks of therapy. The significant correlation (P < 0.0001) between negative parasitological findings and sustained clinical response supports the findings of efficacy. Responders had a higher mean CD4 T-cell counts than non-responders, and non-responders were nearly twice as likely as responders to discontinue the study because of AIDS-related illness or death, to die during the course of the study because of an AIDS complication, or to have an AIDS-related serious adverse event during the treatment. These results are consistent with findings from the two double-blind placebo-controlled studies described above.
The compassionate use study provided the important data related to safety of nitazoxanide administered over the long durations of time at doses up to 3000 mg/day. The median duration of treatment in this study was 62 days with 60 patients receiving more than 6 months of treatment (maximum 4 years). No significant safety concerns have been identified by using these doses or durations of the treatment. Side-effects were usually related to the gastrointestinal tract (nausea, abdominal pain and diarrhoea) and were difficult to distinguish from the symptoms of the disease.
The clinical testing of nitazoxanide in AIDS-related cryptosporidiosis has proven to be a quite a challenge because of difficulties in identifying sufficient numbers of patients with AIDS-related cryptosporidiosis and recruiting these very ill patients for participation in a placebo-controlled clinical trial. In this context, the data generated by this compassionate use study are likely to be important to patients, physicians and caregivers confronted with the challenging task of managing this disease.
Results of controlled clinical trials confirmed by this large compassionate use program support the effectiveness and safety of nitazoxanide in patients with AIDS-related cryptosporidiosis. These studies indicate that the drug should be administered 500 mg b.d. until clinical symptoms resolve and oocysts are eliminated from the stool. Doses may be escalated to 1000 mg b.d. to accelerate or improve parasitological response. Fourteen days of treatment are generally sufficient in patients with CD4 counts above 50 cells/mm3 while at least 8 weeks of treatment are likely required in patients with CD4 counts below 50 cells/mm3.