A phase I dose escalation study of S-1 with concurrent radiotherapy in elderly patients with esophageal cancer

Background

Concurrent chemoradiotherapy (CRT) with 5-fluorouracil (5-FU) and cisplatin (CDDP) are often associated with significant incidence of toxic effects in elderly patients with esophageal cancer. This phase I trial was designed to determine the maximum tolerated dose (MTD) and dose-limiting toxicity (DLT) of S-1, an oral 5-FU derivative, when given with radiotherapy in elderly patients.

Methods

Patients who were age of 70 years or older with histologically confirmed esophageal cancer, and had an Eastern Cooperative Oncology Group (ECOG) score of 0–2 were eligible for this study. Radiotherapy was administered in 1.8 Gy fractions 5 times weekly to a total dose of 54 Gy. S-1 was administered on days 1–14 and 29–42 at the following dosages: 60, 70, and 80 mg/m²/day. Trial registration: {"type":"clinical-trial","attrs":{"text":"NCT01175447","term_id":"NCT01175447"}}NCT01175447 (ClinicalTrials.gov).

Results

Twelve previously untreated patients were enrolled in this study. No grade 3 or 4 toxicity was observed in six patients treated at the 60 and 70 mg/m² dose levels. DLT was observed in four of six patients treated at the 80 mg/m² dose level. Two patients developed grade 3 esophagitis, one patient developed grade 3 esophagitis and pneumonitis, and one patient developed grade 3 thrombocytopaenia. Endoscopic complete response (CR) was observed in eight patients (66.7%). The median progression free survival (PFS) was 20 months and median overall survival was 29 months.

Conclusions

The MTD of S-1 was 80 mg/m², and the recommended dose (RD) for phase II studies was 70 mg/m². This regimen was well tolerated and active in elderly patients with esophageal cancer, meriting further investigation in phase II studies.     

Phase I/II study of dasatinib in combination with decitabine in patients with accelerated or blast phase chronic myeloid leukemia

Treatment of advanced-phase chronic myeloid leukemia (CML) remains unsatisfactory. Single-agent tyrosine kinase inhibitors have modest and short-lived activity in this setting. We conducted a phase I/II study to determine safety and efficacy of the combination of dasatinib and decitabine in patients with advanced CML. Two different dose schedules were investigated with a starting decitabine dose of either 10 mg/m² or 20 mg/m² daily for 10 days plus dasatinib 100 mg daily. The target dose level was decitabine 10 mg/m² or 20 mg/m² daily for 10 days plus dasatinib 140 mg daily. Thirty patients were enrolled, including seven with accelerated-phase CML, 19 with blast-phase CML, and four with Philadelphia-chromosome positive acute myeloid leukemia. No dose-limiting toxicity was observed at the starting dose level with either schedule. Grade ≥3 treatment emergent hematological adverse events were reported in 28 patients. Thirteen patients (48%) achieved a major hematologic response and six (22%) achieved a minor hematologic response, with 44% of these patients achieving a major cytogenetic response and 33% achieving a major molecular response. Median overall survival (OS) was 13.8 months, with significantly higher OS among patients who achieved a hematologic response compared to non-responders (not reached vs 4.65 months; P < .001). Decitabine plus dasatinib is a safe and active regimen in advanced CML. Further studies using this combination are warranted.     

A phase I study of idarubicin dose escalation with amisfostine and high-dose cytarabine in patients with relapsed acute myelogenous leukemia and myelodysplastic syndromes

BACKGROUND AND OBJECTIVES: Early studies have suggested that increasing doses of anthracycline improve outcome in younger patients with acute myelogenous leukemia (AML), but dose escalation has been precluded by the acute and chronic toxicities of these agents. Amifostine is a cytoprotective compound that has been shown to protect against the acute cytotoxicities of anthracyclines in animal models. We report the results of a phase I study of dose escalation of idarubicin with amifostine and high-dose ara-C in patients with relapsed or refractory AML or myelodysplastic syndrome (MDS). DESIGN AND METHODS: The continuous reassessment method was used to predict the probability of toxicity. RESULTS: Five patients were treated at an idarubicin dose of 18 mg/m2/day x 3, three of whom developed grade 3 diarrhea or mucositis. Subsequently, three additional patients were treated at a dose of 15 mg/m2 x 3 days, all of whom experienced grade 3 diarrhea or mucositis. One patient achieved complete remission (CR rate 12.5%, 95% CI 0-0.52%). INTERPRETATION AND CONCLUSIONS: The addition of amifostine does not allow dose escalation of idarubicin when combined with high-dose ara-C.     

A phase 1, multicenter, open-label, dose escalation study of elotuzumab in patients with advanced multiple myeloma

This multicenter, first-in-human study evaluated the safety, tolerability, and pharmacokinetic and pharmacodynamic properties of the anti-CS1 monoclonal antibody elotuzumab. A standard 3 + 3 design was used to determine maximum tolerated dose; dose-limiting toxicities were assessed during cycle 1. Thirty-five patients with relapsed/refractory multiple myeloma were treated with intravenous elotuzumab at doses ranging from 0.5 to 20 mg/kg every 2 weeks. Patients who achieved at least stable disease after 4 treatments could receive another 4 treatments. No maximum tolerated dose was identified up to the maximum planned dose of 20 mg/kg. The most common adverse events, regardless of attribution, were cough, headache, back pain, fever, and chills. Adverse events were generally mild to moderate in severity, and adverse events attributed to study medication were primarily infusion-related. Plasma elotuzumab levels and terminal half-life increased with dose whereas clearance decreased, suggesting target-mediated clearance. CS1 on bone marrow-derived plasma cells was reliably saturated (≥ 95%) at the 10-mg/kg and 20-mg/kg dose levels. Using the European Group for Bone and Marrow Transplantation myeloma response criteria, 9 patients (26.5%) had stable disease. In summary, elotuzumab was generally well tolerated in this population, justifying further exploration of this agent in combination regimens.     

Phase I study of combination therapy with intravenous cidofovir and oral ganciclovir for cytomegalovirus retinitis in patients with AIDS.

Ganciclovir and cidofovir, two antiviral agents used in the treatment of cytomegalovirus (CMV) retinitis, have a synergistic effect inhibiting CMV replication in vitro. In a phase I study, seven patients with AIDS-related CMV retinitis were treated with cidofovir (5 mg/kg intravenously every 2 weeks) combined with ganciclovir (1 g orally three times a day). During a median of 5.5 months (range, 1-12 months) of combined therapy, only one patient had retinitis progression, and only two of 28 blood cultures (specimens of which were obtained on a monthly basis) yielded CMV. Dose-limiting adverse ocular effects (anterior uveitis [two patients] and hypotony [two patients]) occurred in three of seven patients. The results suggest that combination therapy with intravenous cidofovir and oral ganciclovir (a regimen that does not require indwelling central venous catheter access) might enhance clinical efficacy. Less frequent administration of cidofovir in combination with oral ganciclovir should be prospectively studied to determine if the incidence of treatment-associated toxicity might be reduced.     

Proton and carbon ion radiation therapy for locally advanced pancreatic cancer: A phase I dose escalation study

ObjectiveTo determine the maximum tolerated dose (MTD) of proton and carbon ion radiation therapy (PCRT) for locally advanced pancreatic cancer (LAPC).MethodsA single-institution, phase I dose escalation study was performed. The proton dose of 50.4 GyE in 28 fractions was delivered to clinical target volume, and carbon ion as a boost dose to gross tumor volume escalated from 12 GyE to 18 GyE with 3 GyE per fraction in 3 dose levels. The dose limiting toxicity (DLT) was defined as any treatment-related grade (G)3 or higher of non-hematological toxicity. The MTD was exceeded if ≥2 patients in a dose level developed DLT.ResultsFrom May 2015 to July 2016, ten patients were enrolled, 3 in dose level 1, 4 in dose level 2, and 3 in dose level 3. With a median follow-up of 17.4 months, no patient developed a DLT, and the acute G1-2 of gastrointestinal (GI) and hepatic toxicity occurred in 40% of patients, and G1 of GI late toxicity, in 30%. The median overall survival was 17.3 months.ConclusionHigher than 50.4 GyE could be given by PCRT with slight toxicity and good tolerance for LAPC, and the tumor control and survival had been improved, but not significantly. Better outcome may be achieved using carbon ion radiation therapy with higher biological equivalent dose.     

A phase I dose escalation trial of AXP107-11, a novel multi-component crystalline form of genistein,in combination with gemcitabine in chemotherapy-naive patients with unresectable pancreatic cancer

BackgroundAXP107-11 is a novel, multi-component crystalline form of the naturally occurring compound genistein. AXP107-11 has improved physiochemical properties and oral bioavailability compared to the natural form of genistein, and it is possible that combining AXP107-11 with chemotherapy may increase the effect and reduce chemoresistance. The purpose of this dose escalation phase Ib study was to assess the safety, maximum tolerated dose (MTD) and pharmacokinetics (PK) of AXP107-11 in combination with gemcitabine in treatment-naïve patients with inoperable pancreatic carcinoma.Patients and methodsAXP107-11 was given orally in escalating doses (400 mg–1600 mg daily) in combination with standard gemcitabine treatment (1000 mg/m²/week) for the first seven of eight weeks and thereafter for a maximum of four × four-week treatment cycles. PK, safety, MTD and efficacy of AXP107-11 in combination with gemcitabine were evaluated.ResultsSixteen patients were enrolled and received AXP107-11. The maximum concentration in serum of unconjugated (free) genistein was 1 μM. Neither dose-limiting toxicities (DLTs) nor signs of hematological or non-hematological toxicities related to AXP107-11 were observed over a period ranging from 0.7 to 13.2 months. The median overall survival time was 4.9 months (range 1.5–19.5 months). Seven patients (44%) survived longer than six months and 19% were alive at the one-year follow-up.ConclusionTreatment of pancreatic cancer patients with AXP107-11 in combination with gemcitabine resulted in a favorable PK-profile with high serum levels without signs of either hematological or non-hematological toxicity. Accordingly, we suggest further studies with AXP107-11 in pancreatic cancer patients.     

A prospective,multicenter study of low dose decitabine in adult patients with refractory immune thrombocytopenia

We conducted a prospective, multicenter study to evaluate the efficacy and safety of low-dose decitabine in adult patients with refractory immune thrombocytopenia. Adult patients who did not respond to, did not tolerate, or were unwilling to undergo splenectomy, with either a baseline platelet count less than 30 × 10⁹/L or the presence of bleeding symptoms and further need of ITP-specific treatments, were enrolled. Patients received decitabine at 3.5 mg/m² intravenously for three consecutive days per cycle, for three cycles with a four-week interval between cycles. All patients were assessed every week during the first 12 weeks and at four-week intervals thereafter. We screened 49 patients for eligibility. Four patients were excluded and 45 received decitabine. At the end of decitabine treatment, complete response was achieved in eight patients (17.78%), and partial response was achieved in 15 patients (33.33%). The median time to initial response was 28 days (range, 14-70 days). Furthermore, seven relapsed patients received decitabine retreatment and all showed platelet response, including one complete response and six partial responses. Sustained response rates at 6, 12 and 18 months were 44.44% (20/45), 31.11% (14/45) and 20.0% (9/45), respectively. For responders, immune thrombocytopenia-related symptoms, fatigue, psychological health, fear, and overall quality of life were significantly improved. Adverse events were observed in 13 (28.89%) patients. No serious adverse events were recorded. In conclusion, low dose decitabine is potentially effective and safe in the management of adults with refractory immune thrombocytopenia. This trial is registered with clinicaltrials.gov identifier: NCT01568333.     

A phase I study of combination of intravenous gemcitabine, oxaliplatin, and 5-FU with daily oral thalidomide (GOFT) in metastatic/locally advanced pancreatic carcinoma patients

BACKGROUND/AIMS: The phase I study was to determine the maximum tolerance dose and dose-limiting toxicity of gemcitabine/oxaliplatin/5-FU/thalidomide (GOFT) in patients with advanced pancreatic cancer. METHODOLOGY: Chemotherapy-naive patients with histologically proven locally advanced or metastatic pancreatic cancer were enrolled. Gemcitabine was given in a 1-hour infusion followed by oxaliplatin in a 2-hour infusion on day 1, and 5-FU in a 24-hour infusion on day 2, and oral thalidomide 100mg was given daily after intravenous chemotherapy. This regimen was given every 2 weeks. Dose levels of regimen were: level I: gemcitabine 1000mg/m2 + oxaliplatin 60mg/ m2 + 5-FU 1000mg/m2 + thalidomide 100mg/day, level II: gemcitabine 1000mg/m2 + oxaliplatin 70mg/m2 + 5-FU 1000mg/m2 + thalidomide 100mg/day, level III: gemcitabine 1250mg/m2 + oxaliplatin 60mg/m2 + 5-FU 1000mg/m2 + thalidomide 100mg/day. The NCI-CTC grade 3/4 toxicity was used for dose-limiting toxicity. Maximum tolerance dose was determined after the first two cycles in each patient. RESULTS: There were 6 patients in level I, 6 patients in level II, and 1 patient in level III. One of the 6 patients had DLT in level I (grade 3 infection and vomiting), 2 of 6 patients had DLT in level II (grade 3 leukopenia) and 1 patient in level III had DLT (grade 3 leukopenia and stomatitis). Other toxicities at level I/II were grade 1/2 leukopenia (7 episodes), grade 1/2 anemia (5), grade 1/2 nausea (5), grade 1 diarrhea (2), grade 1 alopecia (2), grade 1 skin (2), grade 1 allergy (1). CONCLUSIONS: The GOFT regimen was well tolerated and showed good treatment effect on the pancreatic cancer. We recommended the dose of level II GOFT regimen for further phase II trial.     

A phase I dose escalation study of multicyclic, dose-intensive chemotherapy with peripheral blood stem cell support for small cell lung cancer

A phase I dose-escalation study of multicyclic, ifosfamide, carboplatin, and etoposide (ICE) with sequential reinfusion of peripheral blood stem cells (PBSCs) was conducted to determine the maximum-tolerated dose (MTD) of ICE. Twenty-four patients with SCLC (LD: 6, ED: 18) were treated with ifosfamide (3000-9000 mg/m2, 24-h infusion), carboplatin (300-400 mg/m2), and etoposide (300 mg/m2) followed by subcutaneous filgrastim (75 microg/day) from day 4 to the day of PBSC collection. PBSC were harvested when the WBC count reached >/=5 x 109/l. The leukapheresis product was cryopreserved and reinfused on day 4 of the next cycle, which was started 48 h after the last PBSC collection. The ifosfamide dose was escalated as follows: 3000 mg/m2 (level 1), 5000 mg/m2 (level 2), 7000 mg/m2 (level 3), 9000 mg/m2 (level 4). Patients with LD were treated with concurrent radiotherapy at 1.5 Gy twice daily for the initial 3 weeks to a total dose of 45 Gy and MTD, defined separately. Patients were evaluated for hematologic and non-hematologic toxicity, actual dose intensities, as well as response to therapy. The maximum-tolerated dose (MTD) was defined as the dose level at which more than 5 days of grade 4 myelo- suppression or non-hematologic toxicity greater than grade 3 developed in two thirds of the patients. For ED cases, MTD was level 4 and the recommended dose of ifosfamide was 7000 mg/m2. For LD cases, the recommended dose of ifosfamide was 5000 mg/m2. The dose limiting toxicity of multicyclic ICE was hemato- logic toxicity and CNS toxicity which manifested as ataxia. Tumor responses were seen in all patients, with 14 patients showing a complete response. The actual total dose-intensity at the recommended dose level was 2.2 and 1.74, for ED and LD, respectively, compared with previously reported ICE regimens. PBSC support for dose-intensive ICE regimen permitted dose escalation of ifosfamide with a mean interval of 16-17 days. We conclude that this regimen is well tolerated, with acceptable hematological and non-hematological toxicity. Bone Marrow Transplantation (2000) 25, 5-11.     

A phase 1 clinical trial of vorinostat in combination with decitabine in patients with acute myeloid leukaemia or myelodysplastic syndrome

Patients with acute myeloid leukaemia (AML) or myelodysplastic syndrome (MDS) may respond to treatment with epigenetic‐modifying agents. Histone deacetylase inhibitors may synergize with hypomethylating agents. This phase 1 dose‐escalation study was designed to determine the maximum tolerated dose, recommended phase 2 dose, safety and tolerability of vorinostat plus decitabine in patients with relapsed/refractory AML, newly‐diagnosed AML, or intermediate‐ to high‐grade MDS. Thirty‐four patients received concurrent therapy with decitabine plus vorinostat and 37 received sequential therapy with decitabine followed by vorinostat. Twenty‐nine patients had relapsed/refractory AML, 31 had untreated AML and 11 had MDS. The target maximum administered dose (MAD) of decitabine 20 mg/m² daily for 5 d plus vorinostat 400 mg/d for 14 d was achieved for concurrent and sequential schedules, with one dose‐limiting toxicity (Grade 3 QTc prolongation) reported in the sequential arm. Common toxicities were haematological and gastrointestinal. Responses were observed more frequently at the MAD on the concurrent schedule compared with the sequential schedule in untreated AML (46% vs. 14%), relapsed/refractory AML (15% vs. 0%) and MDS (60% vs. 0%). Decitabine plus vorinostat given concurrently or sequentially appears to be safe and well‐tolerated. Concurrent therapy shows promising clinical activity in AML or MDS, warranting further investigation.     

Phase 1 study of epigenetic priming with decitabine prior to standard induction chemotherapy for patients with AML

We conducted an open-label phase 1 study exploring the feasibility, safety, and biologic activity of epigenetic priming with decitabine before standard induction chemotherapy in patients with less-than-favorable risk of acute myelogenous leukemia (AML). We directly compared the clinical and DNA-hypomethylating activity of decitabine delivered at 20 mg/m2 by either a 1-hour infusion (Arm A) or a continuous infusion (Arm B) for 3, 5, or 7 days before a single, standard induction with infusional cytarabine (100 mg/m2 for 7 days) and daunorubicin (60 mg/m2 × 3 doses). Toxicity was similar to that of standard induction chemotherapy alone. Although we did not identify a maximum tolerated dose, there was more gastro-intestinal toxicity with 7 days of decitabine priming. Decitabine induced DNA hypomethylation at all dose levels and there was a trend toward greater hypomethylation in CD34(+) bone marrow cells when decitabine was delivered by a short pulse (Arm A). Twenty-seven subjects (90%) responded to therapy: 17 with complete remission (57%) and 10 with partial remission (33%). Of the patients with partial remission to protocol treatment, 8 achieved remission to their next therapy, bringing the overall complete remission rate to 83%. We conclude that epigenetic priming of intensive chemotherapy can be safely delivered in an attempt to improve response rates. This trial was registered at www.clinicaltrials.gov as NCT00538876.     

Intracoronary basic fibroblast growth factor (FGF-2) in patients with severe ischemic heart disease: results of a phase I open-label dose escalation study

OBJECTIVES

Evaluate the safety, tolerability and preliminary efficacy of intracoronary (IC) basic fibroblast growth factor (bFGF, FGF-2).

BACKGROUND

FGF-2 is a heparin-binding growth factor capable of inducing functionally significant angiogenesis in animal models of myocardial ischemia.

METHODS

Phase I, open-label dose-escalation study of FGF-2 administered as a single 20-min infusion in patients with ischemic heart disease not amenable to treatment with CABG or PTCA.

RESULTS

Fifty-two patients enrolled in this study received IC FGF-2 (0.33 to 48 μg/kg). Hypotension was dose-dependent and dose-limiting, with 36 μg/kg being the maximally tolerated dose. Four patients died and four patients had non-Q-wave myocardial infarctions. Laboratory parameters and retinal examinations showed mild and mainly transient changes during the 6-month follow-up. There was an improvement in quality of life as assessed by Seattle Angina Questionnaire and improvement in exercise tolerance as assessed by treadmill exercise testing (510 ± 24 s at baseline, 561 ± 26 s at day 29 [p = 0.023], 609 ± 26 s at day 57 (p < 0.001), and 633 ± 24 s at day 180 (p < 0.001), overall p < 0.001). Magnetic resonance (MR) imaging showed increased regional wall thickening (baseline: 34 ± 1.7%, day 29: 38.7 ± 1.9% [p = 0.006], day 57: 41.4 ± 1.9% [p < 0.001], and day 180: 42.0 ± 2.3% [p < 0.001], overall P = 0.001) and a reduction in the extent of the ischemic area at all time points compared with baseline.

CONCLUSIONS

Intracoronary administration of rFGF-2 appears safe and is well tolerated over a 100-fold dose range (0.33 to 0.36 μk/kg). Preliminary evidence of efficacy is tempered by the open-label uncontrolled design of the study.     

Double-blinded infliximab dose escalation in patients with rheumatoid arthritis

OBJECTIVE: To determine the efficacy, safety and pharmacokinetics of infliximab dose escalation in patients with rheumatoid arthritis (RA) who had an inadequate response to 3 mg/kg infliximab treatment or whose disease flared after initially responding. METHODS: Patients with active RA, despite receiving methotrexate, received infliximab 3 mg/kg at weeks 0, 2, 6 and 14 in one of the three arms of the START trial. Beginning at week 22, patients had their infliximab dose increased in a double-blind fashion in increments of 1.5 mg/kg if the total tender and swollen joint count did not improve by at least 20% from baseline (lack of response) or the improvement at week 22 or later worsened by 50% or more (criterion for flare). RESULTS: Of the 329 evaluable patients, 100 (30.4%) patients required dose escalation at or after week 22 because of flare or lack of response. The majority of patients (>80%) who received up to three dose escalations showed >/=20% improvement in the total tender and swollen joint count after their last dose escalation. Patients who required dose escalations generally had lower preinfusion serum infliximab concentrations than those who did not require them. The incidences of adverse events and serious adverse events for the patients who received dose escalation(s) were similar to those of patients who did not receive dose escalation. CONCLUSION: Fewer than one-third of patients required a dose escalation. The majority of patients showed improvement after receiving increased doses of infliximab, without an increased risk of adverse events.     

A dose escalation trial comparing the combination of diltiazem SR and hydrochlorothiazide with the monotherapies in patients with essential hypertension.

A multicentre, randomised, placebo-controlled parallel group study comparing various doses of the combination diltiazem SR (DTZ SR)/hydrochlorothiazide (HCTZ) with the monotherapies was performed to delineate the optimal antihypertensive dosage of the two drug combinations. The study was carried out in 298 patients with mild to moderate essential hypertension (stable supine diastolic blood pressure, DBP, greater than or equal to 95 and less than or equal to 110 mmHg). After a single-blind placebo lead-in period lasting 4-6 weeks to establish stable baseline BP, the patients were randomised to receive either placebo (n = 75), HCTZ (n = 76), DTZ SR (n = 72), or the combination of DTZ SR/HCTZ (n = 75). There were three 4-week evaluation periods with forced escalation of therapy as follows: HCTZ (6.25, 6.25, 12.5 mg twice daily), DTZ SR (60, 90, 120 mg twice daily), and the combination of DTZ SR/HCTZ (60/6.25, 90/6.25, 120/12.5 mg twice daily). DTZ SR/HCTZ (120/12.5 mg) produced statistically significantly greater reductions in supine DBP compared with each monotherapy and placebo. The lower doses of DTZ SR/HCTZ (60/6.25 mg and 90/6.25 mg) produced statistically significantly greater supine DBP reductions compared with DTZ SR monotherapy and placebo, but not compared with HCTZ monotherapy. A comparison of reduction in supine DBP between evaluation periods demonstrated a dose-response relationship for the combination therapy in reducing BP over the dosage range studied. Adverse clinical and laboratory events were not significantly different between the therapies.(ABSTRACT TRUNCATED AT 250 WORDS)     

Outcomes of infliximab dose escalation in patients with rheumatoid arthritis

Clinical Rheumatology - Dose escalation of infliximab in both primary and secondary nonresponders is widely reported; however, the usefulness of dose escalation has been disputed. The objective of...     

Phase I/II dose escalation and randomized withdrawal study with add-on azodicarbonamide in patients failing on current antiretroviral therapy

BACKGROUND: Azodicarbonamide (ADA), a HIV-1 zinc finger inhibitor, targets a new step in viral replication and cell infectivity. OBJECTIVE: A first phase I/II clinical study of ADA. METHODS: ADA was administered at escalating doses concomitantly with current antiviral therapy during a 3-month open-label period in patients with advanced AIDS and documented virological failure. After 3 months, patients were randomized in a double-blind placebo-controlled withdrawal, ADA being given at the highest tolerated dosage. RESULTS: Fifteen patients with advanced disease failing on combined antiretroviral therapy, 75% of them with proven phenotypic resistance, had a median baseline CD4 cell count of 85 x 10(6) cells/l, CD4/CD8 cell ratio of 0.09 and median plasma RNA viral load of 4.2 log10 copies/ml. Tolerance to ADA was dose dependent and some patients developed nephrolithiasis, glucose intolerance or showed an ADA-related cytotoxicity towards CD4 cells at higher dosages. No patient died during the study period. ADA increased CD4 cell percentage, increased the CD4/CD8 cell ratio and decreased plasma RNA viral load from baseline. At the end of the double-blind period, the ADA group, but not the placebo group, showed a significant response (P < 0.05). No phenotypic resistance to ADA was observed. Overall, 3/11 patients (27%) had consistent viral load reductions > 0.5 log10 copies/ml compared with baseline and 5/ 11 (45%) showed a CD4 cell recovery from baseline > 33%. In responders, ADA induced a median peak increase in CD4 cell percentage change from baseline of 65% (range 47-243%), and viral load decrease of 1.04 log10 copies/ml (range 0.52-1.23). CONCLUSIONS: The maximal tolerated dosage of ADA appears to be 2 g (three times daily). This study provides safety results that will allow larger clinical trials to confirm the preliminary efficacy data.