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High-dose cyclophosphamide has long been used an anticancer agent, a conditioning regimen for hematopoietic stem cell transplantation and as potent immunosuppressive agent in autoimmune diseases including aplastic anemia. High-dose cyclophosphamide is highly toxic to lymphocytes but spares hematopoietic stem cells because of their abundant levels of aldehyde dehydrogenase, the major mechanism of cyclophosphamide inactivation. High dose cyclophosphamide therapy induces durable remissions in most patients with acquired aplastic anemia. Moreover, high-dose cyclophosphamide without hematopoietic stem cell rescue has shown activity in a variety of other severe autoimmune diseases. Here we review the history of cyclophosphamide as is applies to aplastic anemia (AA) and other autoimmune diseases. Included here are the historical data from early patients treated for AA as well as an observational retrospective study in a single tertiary care hospital. This latter component was designed to assess the safety and efficacy of high-dose cyclophosphamide therapy without stem cell rescue in patients with refractory autoimmune diseases. We analyzed fully the 140 patients with severe, progressive autoimmune diseases treated. All patients discussed here received cyclophosphamide, 50 mg/kg per day for 4 consecutive days. Response, relapse and overall survival were measured. Response was defined as a decrease in disease activity in conjunction with a decrease or elimination of immune modulating drugs. Relapse was defined as worsening disease activity and/or a requirement of an increase in dose of, or administration of new, immunosuppressive medications. Hematologic recovery occurred in all patients. The overall response rate of the was 95%, and 44% of those patients remain progression-free with a median follow up time of 36 (range 1–120) months for the 140 patients analyzed together. The overall actuarial and event free survival across all diseases at 60 months is 90.7% and 20.6%, respectively. High- dose cyclophosphamide without stem cell rescue is well-tolerated and induces a high rate of remissions in severe autoimmune diseases.
Cyclophosphamide was synthesized in the late 1950s and remains one of the best characterized and most widely administered anti-cancer agents available; it is also a highly efficacious immunosuppressive agent(16). High dosages of cyclophosphamide [≥ 120 mg/kg (5000 mg/m2) employed over 2 to 4 days] as conditioning for hematopoietic stem cell transplantation (HSCT) was developed by Santos and Owens in the late 1960s(37). They were exploring a replacement for the dual anti-cancer and immunosuppressive properties of total body irradiation (TBI) as a HSCT conditioning regimen, because of concerns and access issues and toxicity concerns. Animal studies showed cyclophosphamide to be a potent immunosuppressive; however, in contrast to total body irradiation, doses sufficient to allow allogeneic engraftment were not myeloablative(37). In 1972, using high dose cyclophosphamide as conditioning, Thomas et al reported the first successful human allogeneic HSCT in a patient with severe aplastic anemia (SAA)(41). Later, reports of autologous hematopoietic recovery in SAA following HSCT with high dose cyclophosphamide conditioning suggested that high dose cyclophosphamide alone may be effective in treating SAA. Indeed, a small pilot study demonstrating durable remissions in seven of ten SAA patients following high dose cyclophosphamide therapy without HSCT gave credulity to this hypothesis(8).
Cyclophosphamide's unique pharmacology is responsible for its significant toxicity against the immune system without damaging hematopoietic stem cells at high doses. Cyclophosphamide is a prodrug that is converted by the liver to 4-hydroxycyclophosphamide and aldophosphamide. These compounds diffuse into cells and are converted into the active alkylating compound, phosphoramide mustard, through simple intracellular decomposition. The major mechanism of cyclophosphamide detoxification appears to be inactivation of aldophosphamide by cellular aldehyde dehydrogenase (38) to form the inert compound, carboxyphosphamide. Cells with high proliferative potential, such as hematopoietic stem cells, are relatively resistant to cyclophosphamide because they express high levels of ALDH(20,22,23). Lymphocytes have low levels of ALDH and are rapidly killed by high doses of cyclophosphamide; therefore, high-dose cyclophosphamide is highly immunosuppressive, but not myeloablative, allowing endogenous hematopoietic stem cells to reconstitute hematopoiesis.
Reasoning that high dose cyclophosphamide without stem cell support can induce durable remissions in one autoimmune disease, SAA, we initiated trials of high dose cyclophosphamide without (HSCT) for other severe refractory autoimmune diseases such as lupus, myasthenia gravis, multiple sclerosis and others. The purpose of this report is to compile our single institutional experience of using high dose cyclophosphamide in over 200 patients. Long term follow up in our SAA patients has recently been reported; hence, the bulk of new data in this report will focus on the use of high dose cyclophosphamide for autoimmune conditions other than SAA.
Aplastic anemia is a rare, bone marrow failure disorder characterized by pancytopenia and a hypocellular bone marrow.(6,45) A bone marrow cellularity of less than 25% and markedly decreased values of at least two of three hematopoietic lineages (neutrophil count < 500 / μl, platelet count < 20,000 / μl and absolute reticulocyte count of < 60,000 / μl) define severe disease (SAA). Death may occur due to infection, hemorrhage, or evolution to clonal disease (myelodysplastic syndromes [MDS], leukemia, and paroxysmal nocturnal hemoglobinuria [PNH]). HSCT from a human leukocyte antigen (HLA)-matched sibling donor can cure most patients with SAA, but fewer than 30% of patients have a suitable HLA-matched sibling. Moreover, the best results with allogeneic HSCT are in children; adults do less well primarily due to complications from graft-versus-host disease (GVHD). Alternative donor transplants (32) also have the potential to cure SAA, but such transplants are usually reserved for second-line therapy because of their high rates of morbidity and mortality. Immunosuppressive therapy is also highly effective for treating SAA and is recommended for SAA patients who lack matched sibling donors or who are not suitable candidates for HSCT. The most commonly administered immunosuppressive regimen is antithymocyte globulin and cyclosporine A (ATG/CsA). ATG/CsA will achieve a hematopoietic response in 60–70% of untreated SAA patients, and the probability of survival at 5 years ranges from 60% to 85%(14,18,36). However, up to 40% of patients eventually relapse and an additional 10 to 40% develop a secondary clonal disease(18,30,36,44).
Autoimmune impairment of hematopoiesis in aplastic anemia was first suggested by Mathe et al., who described autologous hematopoietic improvement in aplastic anemia following partially mismatched HSCT using antilymphocyte globulin as a conditioning regimen(27). Shortly thereafter, several reports of autologous hematopoietic reconstitution in SAA patients after allogeneic HSCT following high dose cyclophosphamide conditioning for SAA were reported, suggesting that high-dose cyclophosphamide alone was capable of treating the disease.(6,8,10) In 1976, a case report in the New England Journal of Medicine, described a patient with aplastic anemia successfully treated with high-dose cyclophosphamide without HSCT(2). In the late 1970s, Dr. Lyle Sensenbrenner initiated the first clinical trial of high dose cyclophosphamide therapy for ten patients with SAA who lacked an HLA-matched sibling donor during a time period where antithymocyte globulin was unavailable(8). Durable complete remissions were achieved by seven patients. One of the complete responders died from the acquired immunodeficiency syndrome 44 months after treatment with high-dose cyclophosphamide. The 6 remaining patients are alive and in continuous complete remission, with a median follow-up of 10.8 years (range. 7.3 to 17.8 years) at the time of publication. The median time to last platelet transfusion and time to 0.5 × 109 neutrophils/L were 85 and 95 days, respectively. None of the complete responders has relapsed or developed a clonal disease. Based upon this encouraging data, a new trial of high dose cyclophosphamide for SAA was initiated at Johns Hopkins in 1996. In contrast to our original trial, this trial included patients who had failed to respond to standard immunosuppressive regimens (e.g., antithymocyte globulin and cyclosporine) and employed the use of granulocyte colony-stimulating factor (G-CSF) to hasten neutrophil recovery. The results of this experience were recently published.(5) A total of 67 patients were enrolled (44 treatment naïve and 23 refractory to immunosuppressive therapy). At 10 years, the overall actuarial survival was 88%, the response rate was 71% with the majority being complete, and the actuarial event-free survival (where death, relapse, MDS, HSCT and PNH requiring treatment are defined as events) was 58% in 44 treatment naïve SAA patients. Patients with refractory severe aplastic anemia fared less well after high dose cyclophosphamide therapy; at 10 years, overall actuarial survival, response, and actuarial event-free survival rates were 62%, 48% and 27%, respectively. For treatment naïve patients, the median time to a neutrophil count of 0.5 × 109/L was 60 (range, 28 to 104) days and the median time to last platelet transfusion was 117 (range, 24 to 640) days. The median time to a neutrophil count of 0.5×109/L was 54 (range, 35 to 119) days and the median time to last platelet transfusion was 103 (range, 51 to 751) days for patients with refractory SAA. The median time to complete remission was 20 (range, 4 to 70) months. In summary, the majority of treatment naïve patients with SAA achieve durable remissions after high dose cyclophosphamide therapy; however, patients who are refractory to standard immunosuppression do less well (Table 1)(1,2,5,8,21,26,42). Based upon the success for use of high dose cyclophosphamide in treating one life-threatening autoimmune disease, SAA, we hypothesized that high dose cyclophosphamide may have activity in treating other severe autoimmune conditions.
High-dose cytotoxic therapy followed by HSCT is an active treatment for severe autoimmune diseases.(9,10,28,43) Autologous HSCT has generally been preferred over allogeneic HSCT because of morbidity and mortality associated with graft-versus-host disease. The European Group for Blood and Marrow Transplantation (EBMT) and European League Against Rheumatism (EULAR) have established a registry to compile the results of phase I/II studies of autologous HSCT for the treatment of autoimmune disease.(43) In the United States, the results of HSCT for the treatment of autoimmune disease are collected by the Center for International Blood and Marrow Transplant Research (CIBMTR)(24). Together, these groups have compiled data on more than 1000 patients. These data have been difficult to interpret because of diverse eligibility criteria among studies for the various autoimmune diseases, the heterogeneity of the conditioning regimens, and the differing stem cell products (bone marrow versus peripheral blood and whether in vitro processing or purging was used to remove autoreactive lymphocytes)(43). A 2009 EBMT report on 900 patients found the 5-year survival was 85% and the progression-free survival 43%, although the rates varied widely according to the type of autoimmune disease(17). The most common autoimmune diseases treated, accounting for roughly 50% of the cases, were multiple sclerosis and systemic sclerosis.
High-dose cyclophosphamide-based, non-myeloablative conditioning regimens were used in over 50% of the HSCT cases reported by EBMT/EULAR and the CIBMTR(10,17,43). A subset analysis between myeloablative and non-myeloablative conditioning regimens demonstrated that myeloablative regimens were associated with an increase in treatment-related mortality and no clear advantage in terms of remission induction and relapse rate(10,17,43). Hence, most investigators now favor non-myeloablative, immunosuppressive conditioning regimens (usually high-dose cyclophosphamide +/− other non-myeloablative agents such as antithymocyte globulin) for HSCT in patients with autoimmune diseases(10,43). Because high-dose cyclophosphamide spares hematopoietic stem cells, our group and others have shown it can be safely administered without stem cell support to patients with SAA and a variety of other severe autoimmune diseases (4,5,7,19,29,35,40). Avoiding stem cell reinfusion has a number of potential advantages for treating autoimmune diseases. Not only do stem cell mobilization, collection, cryopreservation, and reinfusion add to the duration, cost, and toxicity of treatment(12), but the mobilized product also contains numerous effector cells (auto-reactive lymphocytes) that may contribute to relapse. Below, we summarize the results of high dose cyclophosphamide without stem cell rescue in 140 patients with a variety of severe autoimmune diseases.
From August 1996 through December 2009, 140 patients with autoimmune diseases (excluding acquired severe aplastic anemia) were treated with high-dose cyclophosphamide. Some of the patients have been previously reported(15,29,35,40). All protocols were approved by the Institutional Review Board of Johns Hopkins, and all participating patients (or their guardians) provided written informed consent. Patients were recruited from the hematologic, neurologic, dermatologic, gastrointestinal, or rheumatologic clinics of the Johns Hopkins Hospital, Baltimore, Maryland. Inclusion criteria were defined in the original studies(15,29,35,40). Briefly, the heterogeneity of the patients can be seen in Table 2. Patients with systemic lupus erythematosus (SLE) met ≥4 of the revised American College of Rheumatology classification criteria for SLE with moderate-to-severe activity. An additional requirement was lack of response or expected lack of response to moderate- to high-dose corticosteroids, to the equivalent degree of immunosuppression, or to appropriate other treatment. Patients with scleroderma were considered eligible with a diagnosis of diffuse cutaneous scleroderma and evidence of clinically active disease. All patients had to have met the American College of Rheumatology definition of scleroderma. Active disease was defined as having had (a) a history by examination or by the patient's self-report of worsening skin changes during the preceding 3 months; (b) diffuse scleroderma and evidence of other organ system disease progression described as a shift by one level in at least one other organ as defined by the Medsger severity score criteria; (c) diffuse scleroderma with evidence of active interstitial lung disease manifested by either >10% decline from the normal percentage predicted values or baseline values of the forced vital capacity or the diffusing capacity. Patients with Myasthenia gravis (MG) had to have a definite clinical diagnosis of MG, with typical physical findings, response to anticholinesterase agents, and at least some improvement with immunosuppressive or immunomodulatory agents. All patients treated here were selected because their MG was either refractory to multiple immunosuppressive agents or required toxic levels of these agents. The eligible patients with Multiple sclerosis (MS) were those who had failed or refused conventional therapy and had active disease. Exclusion criteria included age >70 years, serum creatinine concentration >3.0 mg/dL, ejection fraction by echocardiogram < 45%, or any underlying malignancy.
High-dose cyclophosphamide (50mg/kg) was administered intravenously for four consecutive days over one hour through a central venous catheter. The dose of cyclophosphamide was based on the lesser of actual or ideal body weight as determined by the Metropolitan Life table. Intravenous mesna (10mg/kg) was administered 30 minutes before, and then 3, 6, and 8 hours after, cyclophosphamide as prophylaxis against hemorrhagic cystitis. Beginning six days after the last dose of cyclophosphamide, patients received granulocyte colony stimulating factor (5 μg/kg/day) until the absolute neutrophil count exceeded 0.5×109/liter.
A serotonin 5-HT3 receptor antagonist such as ondansetron (32 mg) was administered intravenously before each dose of cyclophosphamide. Prophylactic antimicrobial support, consisting of fluconazole (400 mg/day), norfloxacin (400 mg/day), and valacyclovir (500 mg twice per day, if antibodies to herpes simplex virus were present), was given beginning the day after the last dose of cyclophosphamide and continued until the neutrophil count exceeded 0.5×109/liter. Pneumocystis prophylaxis (usually trimethoprim-sulfamethoxazole or dapsone) was administered for 6 months. Packed red blood cell transfusions were administered to maintain a hematocrit level > 25%. Platelet transfusions were administered to maintain a platelet count > 10×109/ liter, and for bleeding and procedures. All blood products were irradiated (>2000 rads) to prevent transfusion associated graft-versus-host-disease.
Response was defined as a decrease in disease activity in conjunction with a decrease or elimination of immune modulating drugs. Definitions of disease activity varied by disease and have been previously reported (15,29,31,35,40,40). Relapse was defined as worsening disease activity and/or a requirement for an increase in dose of, or administration of new, immunosuppressive medications. Hospital days were determined from initial hospitalization for the cyclophosphamide dosing (if that occurred) and then any subsequent inpatient time for neutropenic fever or other complications. The inpatient stays were shortened, or in some cases not required, because the patients had access to an intensive outpatient transplantation clinic at the Sidney Kimmel Comprehensive Cancer Center. The patients were seen in the outpatient transplantation clinic seven days a week through the period of neutropenia, and antibiotics and blood products were administered as necessary. Overall mortality was defined as death from any cause for a patient who had been treated with cyclophosphamide. Treatment-related mortality was defined as death within 90 days of treatment with high dose cyclophosphamide. Event free survival was calculated using the Kaplan-Meier estimate; events include death, relapse or disease progression.
From August 1996 through August 2008, 140 patients with severe autoimmune diseases were treated with high dose cyclophosphamide. All but one patient with multiple sclerosis had received standard immunomodulatory therapy for their disease and were refractory to standard treatment. It is a heterogeneous population of diseases and disease characteristics are shown in Tables 2 and and3.3. The median age at the time of treatment was 40 (range 1 to 70) years. The majority of the patients were Caucasian (75.7%) and female (62.1%.) The mean follow up was 50.1 (range 1–127) months.
There were few unexpected side-effects(15,25,29,34,35,40). Nausea with or without emesis during the treatment period was managed with intravenous and oral antiemetics. All patients experienced temporary alopecia and pancytopenia. Febrile neutropenia requiring admission to the hospital occurred in 53 (43%) patients. Of these 53 patients who developed fever, 33 had at least one readmission for the febrile episode. The mean duration of the hospitalization for febrile neutropenia was 4 days. Hemorrhagic cystitis requiring continuous bladder irrigation occurred in 3 (2%) patients (2 with lupus and 1 with scleroderma). There were no deaths before hematologic recovery, although one patient with scleroderma died on day 51 after cyclophosphamide of pneumonia that developed after hematologic recovery. A patient with lupus and comorbid depression committed suicide 3 months after treatment with high dose cyclophosphamide, presumably unrelated to high-dose cyclophosphamide treatment. Only nine patients have died, most from their underlying disease (Table 4).
Hematopoietic recovery occurred in all patients. Patients achieved an absolute neutrophil count > 500/μL at a median of 13 (range 8–22) days after the last dose of cyclophosphamide. The median duration of neutropenia was 9 (range 4–23) days. The median time to last packed red blood cell transfusion after completion of high dose cyclophosphamide was 13 (range 0–33) days and the median time to last platelet transfusion was 12 (range 0–24) days. The median number of packed red blood cell transfusions was 2 (range 0–27) and the median number of platelet transfusions was 2 (range 0–18.)
The overall response rate to high-dose cyclophosphamide was 95%. Of the 133 patients who responded, 59 remain progression-free with a median follow up time of 36 months (range 1–120). (Figure 1) The overall mean duration of the response was 22 (range 3 –120) months and varied by underlying disease. The response criteria were detailed for each disease and response was defined by the individual provider for the disease of interest. In patients with systemic lupus erythematosus, 90% (36/40) had a response as defined by a partial or complete using the RIFLE scoring system(3). The median duration of response was 12 (range 3– 48) months. Of the 40 patients with SLE, 16 had highly refractory disease and were treated on an open-label study; 24 were treated as part of a randomized trial comparing high-dose cyclophosphamide to monthly intravenous cyclophosphamide in a cohort of patients who were less heavily pretreated. In the randomized study, six of seven patients with neurologic manifestations of their SLE had a complete response; in the patients with renal manifestations only four of ten patients responded to high-dose cyclophosphamide (2 complete and 2 partial responses). Patients on this randomized trial who did not respond to intravenous pulse-dose cyclophosphamide were eligible to cross over to the high dose arm. Interestingly, of the six patients who crossed over to high dose cyclophosphamide, three achieved a complete response(34). In patients with multiple sclerosis, 70.2% (33/47) had a response defined as at least a 1 point improvement on their Expanded Disability Status Scale (EDSS)(13). The median duration of the response was 9 (range 6–42) months. In 32 patients with multiple sclerosis treated with high-dose cyclophosphamide (HiCy) at the Johns Hopkins Hospital since 2008, 50% were female, mean age was 41.7 years and mean duration of treatment of illness was 10.2 years (SD 7.1). The median number of failed medications prior to HiCy was 2.5 (range 0–8). Relapses at the time of treatment ranged from 0–9 per year (median of 2 relapses per year). The annualized relapse rate during follow-up dropped to 0.27 compared to a rate of 1.37 in the 2 years prior to HiCy. With baseline disability ranging from EDSS 1.5–6.5, 20% of patients experienced sustained disability progression defined as an increased EDSS of 1 point or more when baseline EDSS <5.0 or an increase in 0.5 points or more with baseline EDSS≥5.0 The patients with relapsing remitting MS had the most pronounced responses. No patient with a baseline EDSS score >6.5 had a sustained remission. There were two patients with primary progressive disease and neither patient responded to therapy. The one patient with secondary progressive disease achieved a transient one point improvement in his EDSS and has since relapsed(13). All nine patients with autoimmune hemolytic anemia responded as defined by transfusion independence, and only one has relapsed (at 22 months). Two patients with autoimmune hemolytic anemia died in remission; one from complications of graft-versus-host-disease following a matched unrelated donor bone marrow transplant that was performed before the development of his autoimmune hemolytic anemia and one from idiopathic thrombocytopenic purpura that developed 14 months after high dose cyclophosphamide therapy. In the patients with pemphigus, all nine patients had a response as defined by marked improvement in the number of blistering skin lesions and a reduction in their prednisone dosage. The median duration of the response was 24 (range 6–60) months. In patients with myasthenia gravis, 13 of 14 (92.9%) responded as defined by improvement in myasthenia gravis disease activity score.(15) The median duration of the response was 13.5 (range 4–72) months. Patients with anti-acetylcholine receptor antibody, anti-muscle specific kinase antibody or no detectable antibody all responded equally well(15). Small numbers of patients with a variety of other severe autoimmune disorders were also treated (Table 1). All of these miscellaneous autoimmune diseases responded to therapy and 56% remain durable. All three patients with autoimmune enteropathy remain in remission with follow-ups over 36 months. Of the patients with immune thrombocytopenic purpura, three of four remain disease-free with a median follow-up of 40 months.
The overall actuarial and event free survival across all diseases at 60 months is 90.7% (95% CI 84.8%–97.1%) and 20.6% (95% CI 13.3%–32.0%), respectively (Figures 1 and and2).2). Figures 3–9 demonstrate the event free survival by disease category. The actuarial event-free survival at 60 months is 10.6% (4.2–26.7%) for patients with systemic lupus erythematosus, 33.2% (8.1–100%) for patients with multiple sclerosis, 32.1% (16.0–64.2%) for patients with myasthenia gravis, 47.1% (24.3–91.4%) for patients with autoimmune hemolytic anemia, 0% for patients with pemphigus, and 22.7% (4.9–100%) for patients with the other autoimmune diseases.
High dose cyclophosphamide leads to durable remissions in the majority of patients with severe aplastic anemia. The results from over 100 SAA patients treated with high dose cyclophosphamide have been reported in the medical literature with roughly 3/4 of the patients from Johns Hopkins. These data demonstrate that the response rate in treatment naïve patients is 70% with the majority of responders achieving a complete remission (normalization of peripheral blood counts). Relapse and secondary clonal disorders (PNH and MDS) may occur; however, these appear to be rare events. Overall and event-free survival are less in patients with refractory severe aplastic anemia and the risk of fungal infections is increased; however, durable remission have been described in roughly 25% of patients.
These data suggest that high-dose cyclophosphamide should be considered, along with the accepted standard of HSCT and ATG/CSA, as treatment considerations for severe aplastic anemia. Each therapy has inherent advantages and disadvantages (Table 5), yet the early mortality (within 6 months of treatment) for all three is 10 –15% and the 5-year survival roughly 80%. The ideal therapy for SAA would be available to all patients, have a low toxicity profile, restore normal hematopoiesis without dependency on long term medical therapy (drug-free remission) and eliminate the risk for late clonal disorders such as PNH and MDS. Thus, treatment decisions must be based on both early toxicity and late complications from the disease. Allogeneic HSCT from a matched sibling remains the most appropriate therapy for children and young adults with SAA; it restores hematopoiesis in less than 4 weeks and cures the disease in more than 80% of cases.(33,39) Relapse and secondary clonal disorders are rare following allogeneic HSCT for SAA. For patients who are not suitable candidate for HSCT both ATG/CSA and high dose cyclophosphamide are reasonable options. Both have response rates of 70%. Our phase II data suggests that the relapse rate and the risk for secondary clonal disorders may be lower following high dose cyclophosphamide than with ATG/CSA, but this will need to be tested in randomized controlled clinical trials.
Our data also suggest that high dose cyclophosphamide is also effective in treating other severe refractory autoimmune diseases. Many investigators have questioned the safety of this approach, largely out of concern for the potential of protracted low blood counts that could lead to unacceptable morbidity and mortality(10,43). In this report of 140 patients receiving high-dose cyclophosphamide for autoimmune diseases, hematopoietic recovery was not delayed by the omission of autologous stem cell rescue. The median of 9 days with an absolute neutrophil count below 0.5 × 109/L and 13 days to transfusion independence is similar to that seen after autologous stem cell rescue. Febrile neutropenia occurred in less than 50% of patients and the median number of days in the hospital was 6.The treatment-related mortality of 0.7% in this group of heavily pretreated, refractory autoimmune disease patients also compares favorably to the 5% and 2% transplant-related mortalities reported by the EBMT and the Northwestern Group (11), respectively. The EBMT found that 100 day transplant-related mortality varied by underlying disease. Specifically, they reported a 2% transplant related mortality in patients with multiple sclerosis, 6% in scleroderma, 11% in lupus and 1% for rheumatoid arthritis. We observed no treatment-related mortality in the lupus (n = 40) or multiple sclerosis patients (n = 47).
The overall response rate to high-dose cyclophosphamide was 94%, with 46% of patients still in remission at the time of this report. The median duration of response was 15 months, but remissions lasting five years or more occurred in more than 20% of patients. These results are comparable to the 5 year overall survival of 85% and progression-free survival of 43% after HSCT reported by the EBMT. We used a rigorous definition of relapse --worsening disease activity from the point of improvement (not baseline) and/or a requirement of an increase in dose or administration of a new immunosuppressive medication. Thus, many of our patients classified as relapsed have not had progression of their disease from baseline. The durability of response after high-dose cyclophosphamide seemed to depend upon the underlying autoimmune disease. More patients with autoimmune hemolytic anemia and multiple sclerosis achieved a durable response than did patients with pemphigus or lupus. However, since the number of patients with each individual disease is small, and most were refractory to other treatments, it is unclear whether this is truly a difference in activity against individual diseases or whether this reflects severity of the disease at the time of treatment.
Selection of patients with severe autoimmune diseases for high dose cyclophosphamide treatment has been better defined by this series. Our data suggest that high dose cyclophosphamide is not superior to monthly pulse dose cyclophosphamide and we do not recommend the use of high dose cyclophosphamide as front-line therapy in SLE. Nevertheless, high-dose cyclophosphamide can be effective salvage therapy for patients with refractory SLE, especially those with neurologic manifestations. Additional clinical trials of high dose cyclophosphamide are needed in order to determine whether this therapy should be more widely used for multiple sclerosis. Our data suggests that high dose cyclophosphamide is most effective for patients with relapsing-remitting disease and an EDSS of less than 6.5.
Eliminating stem cell rescue after high dose cyclophosphamide shortens the duration of the procedure by several weeks, and this, coupled with no requirement for stem cell mobilization, collection, and cryopreservation, should also reduce the cost of the procedure. Moreover, avoiding stem cell infusion eliminates the potential of reinfusing autoreactive lymphocytes with the autograft. Mobilized peripheral blood products usually contain at least 109 CD3+ T cells, and current CD34 selection techniques deplete T cells by only three to four logs, which may be insufficient to eliminate autoreactive clones that could reestablish disease. Recently, it has been suggested that the process of HSCT induces fundamental changes to the immune system that induce long term tolerance; however, it is unclear that cryopreserved hematopoietic stem cells are superior to the endogenous stem cells that lead to hematologic recovery after high-dose cyclophosphamide at “resetting” the immune system.
Although both autologous HSCT and high-dose cyclophosphamide without stem cell rescue generate meaningful clinical benefit for patients with advanced/refractory autoimmune diseases, neither is curative for most such patients. The safety and relative ease of delivery of high-dose cyclophosphamide without stem cell rescue may allow this approach to be utilized earlier in autoimmune disease patients, potentially improving effectiveness in these diseases. A randomized trial of high-dose cyclophosphamide versus standard therapy in patients with relapsing-remitting MS is under development, and should help define the ultimate potential of this approach in autoimmunity.
This study was supported in part by the National Institutes of Health (grants P01CA70970 to Dr. Brodsky and 5K12 HL087169-05 to Dr. DeZern.
Disclosures: Dr. Brodsky and Dr. Jones are entitled to a share of royalties received by Johns Hopkins University from Accentia Pharmaceuticals under a licensing agreement for sales of a method of administering high-dose cyclophosphamide. The study reported in this article could affect the value of this method of administering the drug. The terms of this arrangement are being managed by Johns Hopkins University in accordance with its conflict-of-interest policies.
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