Outcomes of younger patients with mantle-cell lymphoma experiencing late relapse (>24 months): the LATE-POD study.

Patients with mantle cell lymphoma (MCL) who experience first relapse/refractoriness can be categorized into early or late progression-of-disease (POD) groups, with a threshold of 24 months from the initial MCL diagnosis. Bruton tyrosine kinase inhibitors (BTKi) are established standard treatment at first relapse, but their effectiveness as compared to chemoimmunotherapy (CIT) in late-POD patients remains unknown. In this international, observational cohort study, we evaluated outcomes amongst patients at first, late-POD beyond 24 months. Patients treated upfront with BTKi were excluded. The primary objective was progression-free survival from time of second-line therapy (PFS-2) of BTKi versus CIT. After accrual, all patients were prospectively followed-up. Overall, 385 late-POD patients were included from 10 countries. Their median age was 59 (range:19-70) years and 77% were males. Median follow-up from time of first relapse was 53 months (range:12-144). Overall, 114 patients had second-line BTKi, while 271 had CIT, consisting of rituximab-bendamustine (R-B, n=101), R-B and cytarabine (R-BAC, n=70), or other regimens (mostly cyclophosphamide-hydroxydaunorubicin-vincristine-prednisone-CHOP- or platinum-based, n=100). The two groups were balanced for clinicopathological features, and median time to first relapse (48 months for both). Overall, BTKi was associated with significantly prolonged median PFS-2 than CIT [not reached-NR vs 26 months, respectively, P=.0003], and overall survival [NR and 56 months, respectively, P=.03]. Multivariate analyses showed that BTKi was associated with lower risk of death than R-B and other regimens (hazard ratio-HR, 0.41 for R-B, 0.46 for others), but similar to R-BAC. These results may establish BTKi as the preferable second-line approach in BTKi-naïve MCL patients.

PET-based radiomics signature can predict durable responses to CAR T-cell therapy in patients with large B-cell lymphoma.

Chimeric antigen receptor (CAR) T-cell therapy is a promising treatment option for relapsed or refractory (R/R) large B-cell lymphoma (LBCL). However, only a subset of patients will present long-term benefit. In this study, we explored the potential of PET-based radiomics to predict treatment outcomes with the aim of improving patient selection for CAR T-cell therapy. We conducted a single-center study including 93 consecutive R/R LBCL patients who received a CAR T-cell infusion from 2018 to 2021, split in training set (73 patients) and test set (20 patients). Radiomics features were extracted from baseline PET scans and clinical benefit was defined based on median progression-free survival (PFS). Cox regression models including the radiomics signature, conventional PET biomarkers and clinical variables were performed for most relevant outcomes. A radiomics signature including 4 PET-based parameters achieved an AUC = 0.73 for predicting clinical benefit in the test set, outperforming the predictive value of conventional PET biomarkers (total metabolic tumor volume [TMTV]: AUC = 0.66 and maximum standardized uptake value [SUVmax]: AUC = 0.59). A high radiomics score was also associated with longer PFS and OS in the multivariable analysis. In conclusion, the PET-based radiomics signature predicted efficacy of CAR T-cell therapy and outperformed conventional PET biomarkers in our cohort of LBCL patients.

A gene expression assay based on chronic lymphocytic leukemia activation in the microenvironment to predict progression.

Several gene expression profiles with a strong correlation with patient outcomes have been previously described in chronic lymphocytic leukemia (CLL), although their applicability as biomarkers in clinical practice has been particularly limited. Here we describe the training and validation of a gene expression signature for predicting early progression in patients with CLL based on the analysis of 200 genes related to microenvironment signaling on the NanoString platform. In the training cohort (n = 154), the CLL15 assay containing a 15-gene signature was associated with the time to first treatment (TtFT) (hazard ratio [HR], 2.83; 95% CI, 2.17-3.68; P < .001). The prognostic value of the CLL15 score (HR, 1.71; 95% CI, 1.15-2.52; P = .007) was further confirmed in an external independent validation cohort (n = 112). Notably, the CLL15 score improved the prognostic capacity over IGHV mutational status and the International Prognostic Score for asymptomatic early-stage (IPS-E) CLL. In multivariate analysis, the CLL15 score (HR, 1.83; 95% CI, 1.32-2.56; P < .001) and the IPS-E CLL (HR, 2.23; 95% CI, 1.59-3.12; P < .001) were independently associated with TtFT. The newly developed and validated CLL15 assay successfully translated previous gene signatures such as the microenvironment signaling into a new gene expression-based assay with prognostic implications in CLL.

Ibrutinib improves survival compared with chemotherapy in mantle cell lymphoma with central nervous system relapse.

Central nervous system (CNS) relapse of mantle cell lymphoma (MCL) is a rare phenomenon with dismal prognosis, where no standard therapy exists. Since the covalent Bruton tyrosine kinase (BTK) inhibitor ibrutinib is effective in relapsed/refractory MCL and penetrates the blood-brain barrier (BBB), on behalf of Fondazione Italiana Linfomi and European Mantle Cell Lymphoma Network we performed a multicenter retrospective international study to investigate the outcomes of patients treated with ibrutinib or chemoimmunotherapy. In this observational study, we recruited patients with MCL with CNS involvement at relapse who received CNS-directed therapy between 2000 and 2019. The primary objective was to compare the overall survival (OS) of patients treated with ibrutinib or BBB crossing chemotherapy. A propensity score based on a multivariable binary regression model was applied to balance treatment cohorts. Eighty-eight patients were included. The median age at study entry was 65 years (range, 39-87), 76% were males, and the median time from lymphoma diagnosis to CNS relapse was 16 months (range, 1-122). Patients were treated with ibrutinib (n = 29, ibrutinib cohort), BBB crossing chemotherapy (ie, high-dose methotrexate ± cytarabine; n = 29, BBB cohort), or miscellaneous treatments (n = 30, other therapy cohort). Both median OS (16.8 vs 4.4 months; P = .007) and median progression-free survival (PFS) (13.1 vs 3.0 months; P = .009) were superior in the ibrutinib cohort compared with the BBB cohort. Multivariable Cox regression model revealed that ibrutinib therapeutic choice was the strongest independent favorable predictive factor for both OS (hazard ratio [HR], 6.8; 95% confidence interval [CI], 2.2-21.3; P < .001) and PFS (HR, 4.6; 95% CI, 1.7-12.5; P = .002), followed by CNS progression of disease (POD) >24 months from first MCL diagnosis (HR for death, 2.4; 95% CI, 1.1-5.3; P = .026; HR for death or progression, 2.3; 95% CI, 1.1-4.6; P = .023). The addition of intrathecal (IT) chemotherapy to systemic CNS-directed therapy was not associated with superior OS (P = .502) as the morphological variant (classical vs others, P = .118). Ibrutinib was associated with superior survival compared with BBB-penetrating chemotherapy in patients with CNS relapse of MCL and should be considered as a therapeutic option.

IBRORS-MCL study: a Spanish retrospective and observational study of relapsed/refractory mantle-cell lymphoma treated with ibrutinib in routine clinical practice.

This retrospective study evaluated 66 patients diagnosed with relapsed and/or refractory mantle cell lymphoma (R/R MCL) treated with ibrutinib in Spain in routine clinical practice. At diagnosis, patients had a median age of 64.5 years, 63.6% presented with intermediate/high sMIPI (simplified prognostic index for advanced-stage mantle cell lymphoma), 24.5% had the blastoid variant, and 55.6% had a Ki67 > 30%. Patients had received a median of 2 prior lines of therapy (range 1-2; min-max 1-7). Overall response rate was 63.5%, with 38.1% of patients achieving complete response (CR). With a median duration of ibrutinib exposure of 10.7 months (range 5.2-19.6; min-max 0.3-36), the median progression-free survival (PFS) and overall survival (OS) were 20 months [95% confidence interval (CI) 8.8-31.1] and 32 months (95% CI 22.6-41.3), respectively, and were not reached in patients achieving CR. No grade ≥ 3 cardiovascular toxicity or bleeding was reported. This study supports that treatment with ibrutinib leads to high response rates and favorable survival outcomes in patients with R/R MCL.

Regulation of B-Cell Receptor Signaling and Its Therapeutic Relevance in Aggressive B-Cell Lymphomas.

The proliferation and survival signals emanating from the B-cell receptor (BCR) constitute a crucial aspect of mature lymphocyte's life. Dysregulated BCR signaling is considered a potent contributor to tumor survival in different subtypes of B-cell non-Hodgkin lymphomas (B-NHLs). In the last decade, the emergence of BCR-associated kinases as rational therapeutic targets has led to the development and approval of several small molecule inhibitors targeting either Bruton's tyrosine kinase (BTK), spleen tyrosine kinase (SYK), or phosphatidylinositol 3 kinase (PI3K), offering alternative treatment options to standard chemoimmunotherapy, and making some of these drugs valuable assets in the anti-lymphoma armamentarium. Despite their initial effectiveness, these precision medicine strategies are limited by primary resistance in aggressive B-cell lymphoma such as diffuse large B-cell lymphoma (DLBCL) and mantle cell lymphoma (MCL), especially in the case of first generation BTK inhibitors. In these patients, BCR-targeting drugs often fail to produce durable responses, and nearly all cases eventually progress with a dismal outcome, due to secondary resistance. This review will discuss our current understanding of the role of antigen-dependent and antigen-independent BCR signaling in DLBCL and MCL and will cover both approved inhibitors and investigational molecules being evaluated in early preclinical studies. We will discuss how the mechanisms of action of these molecules, and their off/on-target effects can influence their effectiveness and lead to toxicity, and how our actual knowledge supports the development of more specific inhibitors and new, rationally based, combination therapies, for the management of MCL and DLBCL patients.

A phase-II study of atezolizumab in combination with obinutuzumab or rituximab for relapsed or refractory mantle cell or marginal zone lymphoma or Waldenström's macroglobulinemia.

We report efficacy, safety and biomarker data from a phase-II study evaluating atezolizumab (eight 21-day cycle as induction therapy) in combination with obinutuzumab in patients with relapsed/refractory mantle cell lymphoma (MCL, n = 30) or Waldenström's macroglobulinemia (WM, n = 4), and in combination with rituximab in patients with marginal zone lymphoma (MZL, n = 21). All patients received atezolizumab monotherapy as maintenance for ≤10 cycles. Objective response rates at end of induction were 16.7% (MCL) and 42.9% (MZL), with no responses in WM. Median duration of response was 6.8 months (range 5.7-not estimable) for MCL and not reached for MZL. Treatment-emergent adverse events (TEAEs) occurred in 93.3%, 95.2% and 100% of MCL, MZL and WM patients, respectively. One fatal TEAE (pneumonia) occurred in each of the MCL and MZL groups. Biomarker analysis highlighted the importance of characterizing the immune environment to optimize efficacy of immunotherapy regimens.Trial registration details: EudraCT: 2016-003579-22.

Ibrutinib in Combination With Rituximab for Indolent Clinical Forms of Mantle Cell Lymphoma (IMCL-2015): A Multicenter, Open-Label, Single-Arm, Phase II Trial.

PURPOSE: The need for an individualized management of indolent clinical forms in mantle cell lymphoma (MCL) is increasingly recognized. We hypothesized that a tailored treatment with ibrutinib in combination with rituximab (IR) could obtain significant responses in these patients. METHODS: This is a multicenter single-arm, open-label, phase II study with a two-stage design conducted in 12 Spanish GELTAMO sites (ClinicalTrials.gov identifier: NCT02682641). Previously untreated MCL patients with indolent clinical forms defined by the following criteria were eligible: no disease-related symptoms, nonblastoid variants, Ki-67 < 30%, and largest tumor diameter ≤ 3 cm. Both leukemic non-nodal and nodal subtypes were recruited. Patients received ibrutinib 560 mg once daily and a total of eight doses of rituximab 375 mg/m2. Ibrutinib could be discontinued after 2 years in the case of sustained undetectable minimal residual disease (MRD). The primary end point was the complete response (CR) rate achieved after 12 cycles according to Lugano criteria. RESULTS: Fifty patients with MCL (male 66%; median age 65 years) were enrolled. After 12 cycles of treatment, 42 (84%; 95% CI, 74 to 94) patients had an overall response, including 40 (80%; 95% CI, 69 to 91) with CR. Moreover, undetectable MRD in peripheral blood was achieved in 87% (95% CI, 77 to 97) of cases. At 2 years, 24 of 35 evaluable patients (69%) could discontinue ibrutinib because of undetectable MRD. Four patients had disease progression; three were non-nodal MCL and carried high genomic complexity and TP53 mutations at enrollment. No unexpected toxicity was seen except one patient with severe aplastic anemia. CONCLUSION: Frontline IR combination achieves a high rate of CRs and undetectable MRD in indolent clinical forms of MCL. Discontinuation seems appropriate in cases with undetectable MRD, except for TP53-mutated cases.

Cellular and humoral immunogenicity of the mRNA-1273 SARS-CoV-2 vaccine in patients with hematologic malignancies.

Recent studies have shown a suboptimal humoral response to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) messenger RNA (mRNA) vaccines in patients diagnosed with hematologic malignancies; however, data about cellular immunogenicity are scarce. The aim of this study was to evaluate both the humoral and cellular immunogenicity 1 month after the second dose of the mRNA-1273 vaccine. Antibody titers were measured by using the Elecsys and LIAISON anti-SARS-CoV-2 S assays, and T-cell response was assessed by using interferon-γ release immunoassay technology. Overall, 76.3% (184 of 241) of patients developed humoral immunity, and the cellular response rate was 79% (184 of 233). Hypogammaglobulinemia, lymphopenia, active hematologic treatment, and anti-CD20 therapy during the previous 6 months were associated with an inferior humoral response. Conversely, age >65 years, active disease, lymphopenia, and immunosuppressive treatment of graft-versus-host disease (GVHD) were associated with an impaired cellular response. A significant dissociation between the humoral and cellular responses was observed in patients treated with anti-CD20 therapy (the humoral response was 17.5%, whereas the cellular response was 71.1%). In these patients, B-cell aplasia was confirmed while T-cell counts were preserved. In contrast, humoral response was observed in 77.3% of patients undergoing immunosuppressive treatment of GVHD, whereas only 52.4% had a cellular response. The cellular and humoral responses to the SARS-CoV-2 mRNA-1273 vaccine in patients with hematologic malignancies are highly influenced by the presence of treatments such as anti-CD20 therapy and immunosuppressive agents. This observation has implications for the further management of these patients.

Prognostic impact of total metabolic tumor volume in large B-cell lymphoma patients receiving CAR T-cell therapy.

Chimeric antigen receptor (CAR) T-cell therapy provides long-term remissions in patients with relapsed or refractory (R/R) large B-cell lymphoma (LBCL). Total metabolic tumor volume (TMTV) assessed by 18F-fluorodeoxyglucose positron emission tomography (18FDG-PET) has a confirmed prognostic value in the setting of chemoimmunotherapy, but its predictive role with CAR T-cell therapy is not fully established. Thirty-five patients with R/R LBCL who received CAR T-cells were included in the study. TMTV and maximum standardized uptake value (SUVmax) were measured at baseline and 1-month after CAR T-cell infusion. Best response included 9 (26%) patients in complete metabolic response (CMR) and 16 (46%) in partial metabolic response (PMR). At a median follow-up of 7.6 months, median PFS and OS were 3.4 and 8.2 months, respectively. A high baseline TMTV (≥ 25 cm3) was associated with a lower PFS (median PFS, 2.3 vs. 8.9 months; HR = 3.44 [95% CI 1.18-10.1], p = 0.02). High baseline TMTV also showed a trend towards shorter OS (HR = 6.3 [95% CI 0.83-47.9], p = 0.08). Baseline SUVmax did not have a significant impact on efficacy endpoints. TMTV and SUVmax values showed no association with adverse events. Metabolic tumor burden parameters measured by 18FDG-PET before CAR T-cell infusion can identify LBCL patients who benefit most from this therapy.

Outcomes in first relapsed-refractory younger patients with mantle cell lymphoma: results from the MANTLE-FIRST study.

Patients with mantle cell lymphoma (MCL) that fail induction treatment represent a difficult-to-treat population, where no standard therapy exists. We evaluated outcomes in patients with first relapsed-refractory (r/r) MCL after upfront high dose cytarabine including standard regimens. Overall survival (OS-2) and progression-free survival (PFS-2) were estimated from the time of salvage therapy. The previously described threshold of 24 months was used to define patients as early- or late-progressors (POD). Overall, 261 r/r MCL patients were included. Second-line regimens consisted of rituximab-bendamustine (R-B, 21%), R-B and cytarabine (R-BAC, 29%), ibrutinib (19%), and others (31%). The four groups were balanced in terms of clinicopathological features. Adjusting for age and early/late-POD, patients treated with R-BAC had significantly higher complete remission (63%) than comparators. Overall, Ibrutinib and R-BAC were associated with improved median PFS-2 [24 and 25 months, respectively], compared to R-B (13) or others (7). In patients with early-POD (n = 127), ibrutinib was associated with inferior risk of death than comparators (HR 2.41 for R-B, 2.17 for others, 2.78 for R-BAC). In patients with late-POD (n = 134), no significant differences were observed between ibrutinib and bendamustine-based treatments. Ibrutinib was associated with improved outcome in early-POD patients.

Intensification treatment based on early FDG-PET in patients with high-risk diffuse large B-cell lymphoma: a phase II GELTAMO trial.

We conducted a multicentre, phase II study of interim positron emission tomography (PET) as a guide to risk-adapted therapy in high-risk patients with newly diagnosed diffuse large B-cell lymphoma (DLBCL). Patients achieving negative fluorodeoxyglucose (FDG)-PET after three courses of R-MegaCHOP (rituximab, cyclophosphamide, doxorubicin, vincristine, prednisone) received three additional courses, whereas PET-positive patients received two courses of R-IFE (rituximab, ifosfamide, etoposide) followed by BEAM (BCNU, etoposide, cytarabine, melphalan) and autologous stem-cell transplantation. The primary endpoint was progression-free survival (PFS). 71 patients (median age 55 years, range 25-69) were enrolled. With a median follow-up of 42·8 months (range 7·2-58·4), the estimated 4-year PFS and overall survival (OS) were 67% and 78%, respectively, for the global series. Patients in complete remission after interim PET (N = 36) had significantly better 3-year PFS than those with partial response (N = 30) [81% vs. 57%, Hazard ratio (HR) = 2·6, 95% confidence interval (CI) = 1·02-6·65] but not a statistically significant longer OS. A retrospective PET central review was done for 51 patients. According to semiquantitative analysis, 3-year PFS (81% vs. 33%; HR = 6·9, 95% CI = 2·35-20·6) and OS (95% vs. 33%, HR = 19·4, 95% CI = 3·89-97·0) were significantly better for negative than for positive interim PET patients. Early PET assessment is valuable for risk stratification in DLBCL; for this purpose semiquantitative evaluation is a better predictor than visual criteria.

Fludarabine, cyclophosphamide and rituximab as first-line treatment in patients with newly diagnosed follicular lymphoma.

UNLABELLED: Fludarabine-based regimens are highly effective as first-line therapy in patients with follicular lymphoma. Nevertheless, noticeable haematological toxicity has been reported using fludarabine-based regimens. AIM: To analyse the combination of low-dose oral fludarabine and cyclophosphamide plus rituximab (FCR) as induction therapy, followed by rituximab as maintenance therapy. METHODS: We retrospectively analysed 73 patients diagnosed with low-grade follicular lymphoma treated with two different schemes: attenuated oral (AO) and standard intravenous (SIV) FCR. RESULTS: Overall response rate (ORR) was 95% (complete response rate, CRR 79.5%, partial response, PR 15.4%). CRR was 84.6% in AO vs. 61.9% in SIV (P = 0.058). 44.4% of patients underwent maintenance therapy. Grade 3-4 toxicities included neutropenia: 65.4%; anaemia: 39.7%; thrombocytopenia: five patients; infectious complications: six patients. There were no treatment-related deaths. 6.8% had a secondary malignancy. Progression-free survival (PFS) was 84.6% at 12 yr. The following variables influenced PFS in multivariate analysis: Hb < 12 g/dL [HR 4.7 (95% CI 1.18-18.6)], response after induction [HR 4.9 (95% CI 1.01-24)] for PR vs. CR and [HR 21.27 (95% CI 4.33-104)] for SD/DP vs. CR. OS was 83.1% at 12 yr. The following variables significantly influenced OS in multivariate analysis: not receiving rituximab as maintenance therapy (HR 10.7 (95% CI 1.4-82.5), increased levels of ß2-microglobulin [HR 5.2 (95% CI 1.16-23.7)]. CONCLUSIONS: FCR allowed us to obtain a high response rate, which translated into promising progression free and overall survival with an acceptable and manageable toxicity profile, especially with the attenuated oral scheme.

Rituximab, used alone or in combination, is superior to other treatment modalities in splenic marginal zone lymphoma.

Splenic marginal zone lymphoma (SMZL) is a rare B-cell malignancy, with no standard treatment other than splenectomy. Rituximab has shown encouraging results. We therefore retrospectively assessed 43 patients from two centres, who received rituximab, either alone or with chemotherapy. All patients responded, 34/43 (79%) achieving a complete response (CR), compared with 3/10 (30%) after chemotherapy without rituximab (P = 0·005). Of these 10 patients, 9 (90%) subsequently achieved a CR after rituximab (P = 0·02). Rituximab monotherapy appeared equally as effective as rituximab combination therapy (90% vs. 79% CR, P = 0·7) with significantly less toxicity (12·5% vs. 83%, P = 0·002). Splenectomized patients were more likely to obtain a CR with rituximab (16/16, 100%) than unsplenectomized patients (18/27, 67%, P = 0·008). Disease-free survival (DFS) at 3 years was better after rituximab than after splenectomy alone [79% (95% confidence interval 60-89) vs. 29% (8-54), Hazard ratio (HR) 0·28 (0·12-0·68), P = 0·003] and better than after chemotherapy without rituximab [25% (4-55), HR 0·21 (0·08-0·51), P = 0·0004]. Survival at 3 years after rituximab was 98%. In summary, the CR and DFS rates after rituximab, given alone or with chemotherapy, were significantly better than after chemotherapy without rituximab in the same patients, with manageable toxicity. Rituximab, with or without splenectomy, should be considered for the treatment of SMZL.

Stage IV and age over 45 years are the only prognostic factors of the International Prognostic Score for the outcome of advanced Hodgkin lymphoma in the Spanish Hodgkin Lymphoma Study Group series.

The International Prognostic Score (IPS) is the most widely used system to date for identifying risk groups for the outcome of patients with advanced Hodgkin lymphoma, although important limitations have been recognized. We analyzed the value of the IPS in a series of 311 patients with advanced classical Hodgkin lymphoma (cHL) (Ann Arbor stage III, IV or stage II with B symptoms and/or bulky masses) treated with first-line chemotherapy including adriamycin (adriamycin, bleomycin, vinblastine, dacarbazine [ABVD] or equivalent variants). In univariate and multivariate analyses, stage IV disease and age ≥ 45 years were the only factors with independent predictive significance for overall survival (OS) (p = 0.002 and p < 0.001, respectively). Stage IV was still significant for freedom from progression (FFP) (p = 0.001) and age ≥ 45 years was borderline significant (p = 0.058). IPS separates prognostic groups, as in the original publication, but this is mainly due to the high statistical significance of stage IV and age ≥ 45 years. Moreover, the combination of these two factors enables a simpler system to be constructed that separates groups with different FFP and OS. In conclusion, in our series, stage IV and age ≥ 45 years are the key prognostic factors for the outcome of advanced cHL.

Clinical and pharmacokinetic data support once-daily low-dose boosted saquinavir (1,200 milligrams saquinavir with 100 milligrams ritonavir) in treatment-naive or limited protease inhibitor-experienced human immunodeficiency virus-infected patients.

We evaluated the plasma and intracellular pharmacokinetics, clinical efficacy, and safety of once-daily low-dose boosted saquinavir (SQVr; 1,200 of saquinavir [SQV] with 100 mg of ritonavir) plus two nucleotide reverse transcriptase inhibitors in treatment-naive or limited protease inhibitor (PI)-experienced human immunodeficiency virus (HIV)-infected patients. A prospective study without entry restrictions on the plasma HIV-RNA (VL) or CD4 cell count was carried out. Plasma and intracellular SQV levels were measured by high-performance liquid chromatography. Efficacy was evaluated by an intention-to-treat analysis; treatment failure was defined as virological failure (a VL of >50 copies/ml after 24 weeks or a confirmed rebound to >50 copies/ml) or interruption for any reason. A total of 151 patients were included in the study (106 of them either had never received PI or had no previous virological failure on PIs) and could be characterized as follows: previous C3 stage, 28.9%; injection-drug users, 69.1%; subjects with chronic viral hepatitis, 53%; and subjects with cirrhosis, 10%. The median baseline CD4 level was 184/mul, and the median VL was 4.8 log(10) copies/ml. Median C(max), area under the concentration-time curve from 0 to 24 h, and C(min) plasma and intracellular SQV levels were 3,672 and 10,105 ng/ml, 34,283 and 99,535 ng.h/ml, and 359 and 1,062 ng/ml, respectively. The efficacy as determined by intention to treat at 52 weeks was 69.7% (96% in the on-treatment analysis), with similar results regardless of the baseline VL and CD4 counts. Only five patients had virological failure despite adequate C(min) levels, but with a poor adherence (the only variable related to virological failure). Adverse events caused the withdrawal of the treatment in four patients (2.6%). In conclusion, given the pharmacokinetic profile, efficacy, and tolerability of this regimen, once-daily low-dose SQVr may be considered a treatment option in treatment-naive or limited PI-experienced HIV-infected patients, with the additional benefit of being currently the least-expensive PI-based regimen available.