Discovery and development of first in class antifungal caspofungin (CANCIDAS®)--a case study.

Covering: 1985 to 2001.This paper describes a fifteen year journey from concept to clinical discovery and development of the first in class caspofungin acetate (CANCIDAS®) a parenteral antifungal agent. Caspofungin is a semisynthetic derivative of pneumocandin B0, a naturally occurring, lipophilic cyclic peptide isolated from the fungus, Glarea lozoyensis. While the echinocandins had been previously studied for antifungal activity by several organizations, the class was dropped for a variety of reasons. Merck subsequently initiated a research program leading to the discovery and development of caspofungin. The multitude of challenges that ensued during the discovery and development process and which were successfully resolved by multi-disciplinary teams constitute the content of this article. The article consists of five sections that describe the discovery and development of caspofungin in chronological order: (i) discovery of the natural product pneumocandin B0 from fungal fermentations, (ii) fermentation development to improve the titer of pneumocandin B0 to make it commercially viable, (iii) semisynthetic modification by medicinal chemistry to successfully improve the properties of pneumocandin B0 leading to the discovery of caspofungin, (iv) development of commercial semisynthesis and purification and formulation development to improve stability and (v) clinical development and approval of CANCIDAS® as an antifungal drug which subsequently saved thousands of lives.

Advances in antifungal therapy.

The prevalence of invasive fungal infections (IFIs) has increased over the past three decades owing to the increasing numbers of immunocompromised hosts. These infections are associated with significant morbidity and mortality. Recent significant advances in antifungal therapy include the broad-spectrum triazoles (voriconazole and posaconazole) and a new class of antifungals, the echinocandins (caspofungin, micafungin, and anidulafungin). New treatment strategies, such as combination therapy and pre-emptive therapy, are being investigated. There have also been significant improvements in diagnostics; the galactomannan enzyme immunoassay and the beta-glucan test are now part of the EORTC/MSG criteria for diagnosis of IFI. Despite these advances, there remain a number of unanswered questions regarding optimal management of serious fungal infections, and research continues to discover and develop new therapies and evaluate new management strategies.

Invasive candidiasis treated in the intensive care unit: observations from a randomized clinical trial.

OBJECTIVES: The objectives of this study were to contrast risk factors, microbiology, and outcomes in patients with invasive candidiasis treated in an intensive care unit (ICU) with those in patients with invasive candidiasis treated outside an ICU and to describe therapeutic results with caspofungin in ICU patients. MATERIALS AND METHODS: We retrospectively identified patients with documented invasive candidiasis who received their first dose of the study drug in the ICU as part of a double-blind randomized trial. Participants were not stratified at entry by their ICU status. Patients received caspofungin (50 mg/d after a 70-mg loading dose) or conventional amphotericin B (0.6-1.0 mg/kg per day) for 10 to 14 days. A favorable response required resolution of signs and symptoms as well as eradication of Candida pathogens. RESULTS: Of the 224 patients, 97 (43%) received their first dose of the study drug in the ICU. Most patients had well-recognized risk factors for invasive candidiasis, including broad-spectrum antibiotics, central venous catheters, and hyperalimentation. Recent surgery was more common whereas malignancy, neutropenia, and immunosuppression were less common among ICU patients than among non-ICU patients. Candidemia was demonstrated in 81% of ICU patients and in 84% of non-ICU patients. Favorable response rates in the ICU patients vs the non-ICU patients were 68% (95% confidence interval [CI] = 53%, 82%) vs 77% (95% CI = 67%, 87%) for caspofungin and 56% (95% CI = 43%, 69%) vs 67% (95% CI = 55%, 79%) for amphotericin B. After accounting for differences in APACHE (Acute Physiology and Chronic Health Evaluation) II score, neutropenia status, and geographic region, we found that patients initiating the study therapy in an ICU were still more likely to die than patients initiating study therapy outside an ICU. For ICU patients, all-cause mortality rates were 45% (95% CI = 30%, 60%) for caspofungin recipients and 40% (95% CI = 28%, 53%) for amphotericin B recipients, whereas candidiasis-attributable mortality rates were 5% (95% CI = 0%, 12%) for caspofungin recipients and 11% (95% CI = 3%, 19%) for amphotericin B recipients. Overall, drug-related adverse events were reported less often among the ICU patients than among the non-ICU patients. CONCLUSIONS: In ICU patients treated with antifungal therapy, invasive candidiasis is associated with substantial mortality, but most deaths cannot be directly attributed to this infection.

Pharmacokinetics, safety, and tolerability of caspofungin in children and adolescents.

Caspofungin is a parenteral antifungal that inhibits beta-1,3-D-glucan synthesis. Although licensed for adult use, the appropriate caspofungin dosing regimen in pediatric patients is not yet known. We therefore investigated the pharmacokinetics and safety of caspofungin in pediatric patients. Thirty-nine children (ages 2 to 11 years) and adolescents (ages 12 to 17 years) with neutropenia were administered caspofungin using either a weight-based regimen (1 mg/kg of body weight/day) or a body surface area regimen (50 mg/m2/day or 70 mg/m2/day). Plasma samples for caspofungin profiles were collected on days 1 and 4. These results were compared to those from adults treated with either 50 or 70 mg/day for mucosal candidiasis. In children receiving 1 mg/kg/day (maximum, 50 mg/day), the area under the concentration-time curve over 24 h (AUC(0-24)) was significantly smaller (46% after multiple doses) than that observed in adults receiving 50 mg/day (P < 0.001). In children and adolescents receiving 50 mg/m2/day (maximum, 70 mg/day), the AUC(0-24) following multiple doses was similar to that for the exposure in adults receiving 50 mg/day. The AUC(0-24) and concentration trough (at 24 h) in pediatric patients receiving the 50-mg/m2 daily regimen were consistent across the range of ages. Caspofungin was generally well tolerated in this study. None of the patients developed a serious drug-related adverse event or were discontinued for toxicity. These results demonstrate that caspofungin at 1 mg/kg/day in pediatric patients is suboptimal. Caspofungin administration at 50 mg/m2/day provides a comparable exposure to that of adult patients treated with 50 mg/day.

Invasive candidiasis in cancer patients: observations from a randomized clinical trial.

BACKGROUND: Invasive candidiasis is a common and serious complication of cancer and its therapy. METHODS: We retrospectively identified patients with malignancies enrolled in a double-blind randomized trial of caspofungin (50 mg/day after a 70 mg loading dose) vs. conventional amphotericin B (0.6-1.0 mg/kg/day) as treatment of documented invasive candidiasis. A favorable response required complete resolution of signs and symptoms plus eradication of the Candida pathogen(s). The primary efficacy analysis used a modified intention-to-treat (MITT) approach that included all patients with a confirmed diagnosis of invasive candidiasis who received > or =1 dose of study medication. RESULTS: 74/224 (33%) patients in the MITT population had active malignancies. 25/30 (83%) hematological malignancies were acute or chronic leukaemias. 22/44 (50%) solid tumors were related to the gastrointestinal tract. Patients with hematological malignancies tended to be younger (median [range] age: 49 [19-74] vs. 59 [19-81] years) and have higher baseline acute physiology and chronic health evaluation (APACHE) II scores (mean [range]: 17 [0-28] vs. 15 [5-35]) than patients with solid tumors. Neutropenia [< or =500/microl] was present on entry in 23 (77%) patients with hematological malignancies and in one (3%) patient with a solid tumor. Candidemia was demonstrated in 56 (88%) cancer patients. C. albicans was the single most frequent isolate in cancer patients, although the majority of cases were caused by non-albicans species. Cancer patients in the caspofungin arm had more hematological malignancies (55 vs. 29%), higher baseline APACHE II scores (>20 in 36 vs. 15%), more frequent neutropenia (42 vs. 24%), and less C. albicans infections (27 vs. 49%) than the amphotericin B-treated cancer patients. Favorable response rates were 11/18 (61%) and 6/12 (50%) for patients with hematological malignancies treated with caspofungin or amphotericin B, respectively; the corresponding outcomes in patients with solid tumors were 12/15 (80%) and 17/29 (59%) for the 2 treatment arms. 7/14 (50%) caspofungin- and 4/10 (40%) amphotericin B-treated patients who were neutropenic on entry responded favorably. All-cause mortality rates during the study for caspofungin recipients were 11/18 (61%) with hematological malignancies and 6/15 (40%) with solid tumors, and for amphotericin recipients were 4/12 (33%) with hematological malignancies and 6/29 (21%) with solid tumors. CONCLUSIONS: Underlying cancers, most commonly leukaemias and gastrointestinal tumors, were present in one-third of patients enrolled in this study of invasive candidiasis. Overall, 70% of caspofungin-treated and 56% of amphotericin B-treated cancer patients responded favorably. Response rates were lower for neutropenic leukaemic patients than for non-neutropenic patients with solid tumors in both treatment groups.

Salvage therapy with caspofungin for invasive aspergillosis: results from the caspofungin compassionate use study.

OBJECTIVES: The objective was to prospectively assess the efficacy and safety of caspofungin as salvage therapy for invasive aspergillosis in patients enrolled in the caspofungin compassionate-use study. METHODS: Forty-eight patients with invasive Aspergillus infections (36 with pulmonary infection, 12 with extrapulmonary or disseminated infection) were enrolled in this study. All patients were refractory to or intolerant of intravenous amphotericin B or a lipid amphotericin formulation(s). Efficacy was assessed at end of intravenous caspofungin therapy based on the clinical (symptom/sign and radiographic) response. RESULTS: Underlying diseases included hematological malignancy (69%), organ transplant (8%), and AIDS (6%). Forty-three (90%) patients were refractory to prior antifungal treatment, including 25 patients refractory to multiple agents. Sixteen (33%) were neutropenic at study entry. Following caspofungin therapy, a favorable response was noted in 44% (20/45) of the patients, including nine (20%) and 11 (24%) patients with complete and partial responses, respectively. Caspofungin was generally well tolerated one serious drug-related adverse event was reported. CONCLUSIONS: In this study, caspofungin was an effective alternative for patients with refractory Aspergillus infections.

Efficacy and safety of caspofungin for treatment of invasive aspergillosis in patients refractory to or intolerant of conventional antifungal therapy.

BACKGROUND: Invasive aspergillosis (IA) is an important cause of morbidity and mortality among immunocompromised patients. Echinocandins are novel antifungal molecules with in vitro and in vivo activity against Aspergillus species. METHODS: We investigated the efficacy and safety of caspofungin in the treatment of IA. Ninety patients with IA who were refractory to or intolerant of amphotericin B, lipid formulations of amphotericin B, or triazoles were enrolled to receive caspofungin. RESULTS: Efficacy was assessed for 83 patients who had infection consistent with definitions of IA and who received >or=1 dose of study drug. Common underlying conditions included hematologic malignancy (48% of patients), allogeneic blood and marrow transplantation (25% of patients), and solid-organ transplantation (11% of patients). Seventy-one patients (86%) were refractory to and 12 patients (14%) were intolerant of previous therapy. A favorable response to caspofungin therapy was observed in 37 (45%) of 83 patients, including 32 (50%) of 64 with pulmonary aspergillosis and 3 (23%) of 13 with disseminated aspergillosis. Two patients discontinued caspofungin therapy because of drug-related adverse events. Drug-related nephrotoxicity and hepatotoxicity occurred infrequently. CONCLUSION: Caspofungin demonstrated usefulness in the salvage treatment of IA.

Caspofungin versus liposomal amphotericin B for empirical antifungal therapy in patients with persistent fever and neutropenia.

BACKGROUND: Patients with persistent fever and neutropenia often receive empirical therapy with conventional or liposomal amphotericin B for the prevention and early treatment of invasive fungal infections. Caspofungin, a member of the new echinocandin class of compounds, may be an effective alternative that is better tolerated than amphotericin B. METHODS: In this randomized, double-blind, multinational trial, we assessed the efficacy and safety of caspofungin as compared with liposomal amphotericin B as empirical antifungal therapy. At study entry, patients were stratified according to risk and according to whether they had previously received antifungal prophylaxis. A successful outcome was defined as the fulfillment of all components of a five-part composite end point. RESULTS: Efficacy was evaluated in 1095 patients (556 receiving caspofungin and 539 receiving liposomal amphotericin B). After adjustment for strata, the overall success rates were 33.9 percent for caspofungin and 33.7 percent for liposomal amphotericin B (95.2 percent confidence interval for the difference, -5.6 to 6.0 percent), fulfilling statistical criteria for the noninferiority of caspofungin. Among patients with baseline fungal infections, a higher proportion of those treated with caspofungin had a successful outcome (51.9 percent vs. 25.9 percent, P=0.04). The proportion of patients who survived at least seven days after therapy was greater in the caspofungin group (92.6 percent vs. 89.2 percent, P=0.05). Premature study discontinuation occurred less often in the caspofungin group than in the amphotericin B group (10.3 percent vs. 14.5 percent, P=0.03). The rates of breakthrough fungal infections and resolution of fever during neutropenia were similar in the two groups. Fewer patients who received caspofungin sustained a nephrotoxic effect (2.6 percent vs. 11.5 percent, P<0.001), an infusion-related event (35.1 percent vs. 51.6 percent, P<0.001), or a drug-related adverse event or discontinued therapy because of drug-related adverse events. CONCLUSIONS: Caspofungin is as effective as and generally better tolerated than liposomal amphotericin B when given as empirical antifungal therapy in patients with persistent fever and neutropenia.

Second-line therapy with caspofungin for mucosal or invasive candidiasis: results from the caspofungin compassionate-use study.

OBJECTIVES: To prospectively assess the efficacy and safety of caspofungin as second-line therapy for mucosal or invasive candidiasis in patients enrolled in the caspofungin compassionate-use study. MATERIALS AND METHODS: Thirty-seven patients with mucosal or invasive candida infections (17 oesophageal, four oropharyngeal and 16 invasive candidiasis) were enrolled in the caspofungin compassionate-use study. All patients were refractory to or intolerant of intravenous amphotericin B or lipid amphotericin formulation(s). Efficacy was assessed at the end of intravenous caspofungin therapy based on clinical (and, where appropriate, microbiological) response. RESULTS: HIV was the most common (91%) risk factor in patients with mucosal candidiasis; patients with invasive candidiasis commonly had acute leukaemia/lymphoma (50%) or diabetes mellitus (31%). Most patients with mucosal candidiasis (91%) and invasive candidiasis (94%) were refractory to >/=1 antifungal agent(s). A favourable response was noted in 82% (14/17) with oesophageal candidiasis, 100% (4/4) with oropharyngeal candidiasis and 87% (13/15) with invasive candidiasis. Caspofungin was generally well tolerated; one serious drug-related adverse event was reported. CONCLUSION: In this study, caspofungin was an effective alternative for patients with refractory candida infections.

A randomized double-blind study of caspofungin versus fluconazole for the treatment of esophageal candidiasis.

BACKGROUND: Candida esophagitis remains an important cause of morbidity in patients with advanced human immunodeficiency virus (HIV) infection. Fluconazole is widely regarded as the treatment of choice for this condition. METHODS: The efficacy and safety of caspofungin were compared with fluconazole in adult patients with Candida esophagitis in a double-blind randomized trial. Eligible patients had symptoms compatible with esophagitis, endoscopic demonstration of mucosal plaques, and microscopic demonstration of Candida from the esophageal lesions. Patients were randomly assigned to receive caspofungin (50 mg) or fluconazole (200 mg) intravenously once daily for 7 to 21 days. The primary endpoint was the combined response of symptom resolution and significant endoscopic improvement 5 to 7 days after discontinuation of treatment. Data were analyzed with a modified intention-to-treat analysis, which excluded 2 ineligible patients. RESULTS: Most patients (154/177; 87%) had HIV infection, with a median CD4 count of 30 cells/mm(3). Candida albicans was the predominant isolate. Favorable response rates were achieved in 66 (81%) of the 81 patients in the caspofungin arm and in 80 (85%) of the 94 patients in the fluconazole arm (difference = -4%; 95% confidence interval: -15% to +8%). Symptoms had resolved in >50% of patients in both groups by the fifth day of treatment. No patient in the caspofungin group developed a serious drug-related adverse event; therapy was only discontinued in 1 patient (receiving fluconazole) due to a drug-related adverse experience. Four weeks after stopping study drug, symptoms had recurred in 18 (28%) of 64 patients given caspofungin and in 12 (17%) of 72 patients given fluconazole (P = 0.19). CONCLUSIONS: In this study, caspofungin appeared to be as efficacious and generally as well tolerated as fluconazole in patients with advanced HIV infection and documented Candida esophagitis.

Efficacy of caspofungin in the treatment of esophageal candidiasis resistant to fluconazole.

Caspofungin is a new echinocandin drug with comparable in vitro activity against azole-susceptible and -resistant isolates of that could provide a less toxic alternative to amphotericin B for the management of esophageal candidiasis with clinical or laboratory evidence of decreased susceptibility to fluconazole. The authors retrospectively analyzed its efficacy in adults with endoscopically documented esophagitis from four Phase II and III studies using two definitions of resistance to fluconazole: 1) clinically refractory infection based on failure of esophageal symptoms to improve despite at least 1 week of >or=200 mg/d of fluconazole; or 2) microbiologically resistant infection with either "susceptible dose-dependent" or "resistant" isolates based on MICs of 16 to 32 and >or=64 microg fluconazole/mL, respectively. A favorable response required resolution of all symptoms and substantial improvement in endoscopic findings. Seven of 11 patients (64%) who had been clinically refractory to fluconazole had favorable responses to caspofungin. Eleven of 14 patients (79%) whose isolates had decreased susceptibility to fluconazole had favorable responses to caspofungin, including 5 (83%) of 6 patients infected by isolates with MICs of >or=64 microg fluconazole/mL. Caspofungin appeared to be efficacious therapy for some patients with esophageal candidiasis who were clinically refractory to fluconazole or infected by with reduced susceptibility to fluconazole in vitro.

Response and relapse rates of candidal esophagitis in HIV-infected patients treated with caspofungin.

Caspofungin is a new antifungal drug of the echinocandin class. We analyzed the clinical efficacy of caspofungin (50 mg/day) in the treatment of HIV-infected adults with endoscopically documented Candida esophagitis and enrolled in four clinical trials of caspofungin. Symptoms were evaluated daily; a favorable outcome required complete resolution of all esophageal symptoms assessed at the time of discontinuation of therapy. Relapse was defined as recurrent symptoms during the subsequent 2 weeks. A multivariate logistic regression model was developed to identify potential factors (including severity of symptoms at presentation, CD4(+) cell count on entry, extent of disease [assessed endoscopically at baseline], causative Candida species, duration of therapy [overall and after resolution of symptoms], time on treatment before symptom resolution, and antifungal prophylaxis) that might predict symptomatic relapse in the 2 weeks following completion of therapy. The median CD4(+) lymphocyte count for the entire population was 31/mm(3). Candida albicans was isolated from 109 of 110 patient samples cultured for the pathogen and constituted the sole isolate in 77%. Extensive esophageal involvement was present in 55% of patients at the time of pretreatment endoscopy. The duration of therapy ranged from 7 to 20 days (median, 12 days). Symptoms resolved in 117 of 123 patients (95%; 95% confidence interval, 90-98%) with a median time of ~4 days. Response rates were 43 of 46 (93%) and 70 of 73 (96%) for patients with greater or fewer than 50 CD4(+) cells/mm(3), and 80 of 85 (94%) and 23 of 24 (96%) in infections caused by C. albicans alone or in association with non-albicans isolates, respectively. Symptoms recurred within 2 weeks of stopping caspofungin in 19 of 115 evaluable patients (17%), including 3 of 16 (19%) receiving antifungal prophylaxis. Relapse rates were similar for patients with greater or fewer than 50 CD4(+) cells/mm(3). In this relatively small number of patients, only symptom severity and extent of disease judged endoscopically at baseline were significantly (p < 0.10) associated with early relapse in the multivariate model.

Randomized, double-blind, multicenter study of caspofungin versus amphotericin B for treatment of oropharyngeal and esophageal candidiases.

Caspofungin is an antifungal agent of the novel echinocandin class. We investigated its efficacy, safety, and tolerability as therapy for oropharyngeal and/or esophageal candidiasis in a phase II dose-ranging study. Patients were randomized in a double-blind manner to receive either caspofungin acetate (35, 50, or 70 mg) or amphotericin B (0.5 mg/kg of body weight) intravenously once daily for 7 to 14 days. A favorable response required both complete resolution of symptoms and quantifiable improvement of mucosal lesions 3 to 4 days after discontinuation of study drug. Efficacy was assessed using a modified intent-to-treat analysis. No hypothesis testing of efficacy was planned or performed. Of 140 enrolled patients, 63% had esophageal involvement and 98% were infected with the human immunodeficiency virus (HIV) (median CD4 count, 30/mm(3)). A modestly higher proportion of patients in each of the caspofungin groups (74 to 91%) achieved favorable responses compared to amphotericin B recipients (63%), but there was considerable overlap in the 95% confidence intervals surrounding these point estimates. Similar trends were found in the subgroups with esophageal involvement, a history of fluconazole failure, and CD4 counts of < or =50/mm(3). A smaller proportion of patients receiving any dose of caspofungin experienced drug-related adverse events compared to patients given standard doses of conventional amphotericin B (P < 0.01). Caspofungin provided a generally well-tolerated parenteral therapeutic option for HIV-infected patients with oropharyngeal and/or esophageal candidiasis in this study.