Response-adapted, time-limited venetoclax, umbralisib, and ublituximab for relapsed/refractory chronic lymphocytic leukemia.

ABSTRACT: Many patients with chronic lymphocytic leukemia (CLL) will develop treatment resistance to Bruton tyrosine kinase (BTK) inhibitors. Phosphatidylinositol-3-kinase (PI3K) inhibitors, including umbralisib, have significant clinical activity in relapsed/refractory CLL, but prolonged exposure is associated with potential toxicities. Owing to the synergistic antitumor effects of combined PI3K and BCL-2 inhibition, we sought to explore the feasibility of response-adapted, time-limited therapy to optimize disease control while mitigating the risks of prolonged treatment. We conducted a phase 1/2 clinical trial to determine the safety and efficacy of venetoclax in combination with umbralisib and the anti-CD20 monoclonal antibody, ublituximab, (U2-VeN) in patients with relapsed/refractory CLL (N = 46) and Richter transformation (N = 5). After 12 cycles, treatment was stopped for patients with CLL who achieved undetectable minimal residual disease (uMRD). Adverse events of special interest included diarrhea in 50% of patients (11% grade 3/4), and aspartate aminotransferase and/or alanine aminotransferase elevation in 15 patients (33%), with 3 (7%) grade 3/4. There were no cases of tumor lysis syndrome related to venetoclax, with outpatient initiation in 96% of patients. The intent-to-treat overall response rate for CLL was 98% with best response of 100% in evaluable patients (42% complete responses). The end-of-treatment rate of uMRD at 10-4 in bone marrow was 77% (30/39), including a 71% uMRD rate among 14 patients refractory to prior BTK inhibitor. Time-limited venetoclax and U2 is safe and highly effective combination therapy for patients with relapsed/refractory CLL including those who have been previously treated with covalent BTK inhibitors. This trial was registered on www.clinicaltrials.gov as #NCT03379051.

Patient-reported impact of symptoms in lung cancer (PRISM-LC).

Background: Individuals with lung cancer (LC) face a variety of symptoms that significantly impact their lives. We use extensive patient input to determine the relative importance and prevalence of these symptoms and identify which demographic features are associated with a higher level of disease burden. Methods: We performed semi-structured qualitative interviews with participants with LC to identify potentially important symptoms. We then conducted a cross-sectional study, in which participants rated the relative importance of 162 individual symptoms covering 14 symptomatic themes. Participant responses were analyzed by age, sex, disability status, disease duration, LC stage, type of treatment received, and smoking history, among other categories. Results: Our cross-sectional study had 139 participants with LC. The most prevalent symptomatic themes reported by this population were fatigue (85.5%), impaired sleep and daytime sleepiness (73.5%), and emotional issues (73.0%). The symptomatic themes that had the greatest average impact (on a scale of 0 to 4, with 4 being the most impactful) were social role dissatisfaction (1.67), inability to do activities (1.64), and fatigue (1.60). Disability status had the strongest association with symptomatic theme prevalence. LC stage (stage IV), receipt of therapy, and smoking experience were also associated with higher frequency of symptomatic themes. Conclusions: Individuals with LC face diverse and disease-specific symptoms that affect their daily lives. Patient insight on the prevalence and relative importance of these symptoms is invaluable to advance meaningful therapeutic interventions.

Heterogeneity of neuroendocrine transcriptional states in metastatic small cell lung cancers and patient-derived models.

Molecular subtypes of small cell lung cancer (SCLC) defined by the expression of key transcription regulators have recently been proposed in cell lines and limited number of primary tumors. The clinical and biological implications of neuroendocrine (NE) subtypes in metastatic SCLC, and the extent to which they vary within and between patient tumors and in patient-derived models is not known. We integrate histology, transcriptome, exome, and treatment outcomes of SCLC from a range of metastatic sites, revealing complex intra- and intertumoral heterogeneity of NE differentiation. Transcriptomic analysis confirms previously described subtypes based on ASCL1, NEUROD1, POU2F3, YAP1, and ATOH1 expression, and reveal a clinical subtype with hybrid NE and non-NE phenotypes, marked by chemotherapy-resistance and exceedingly poor outcomes. NE tumors are more likely to have RB1, NOTCH, and chromatin modifier gene mutations, upregulation of DNA damage response genes, and are more likely to respond to replication stress targeted therapies. In contrast, patients preferentially benefited from immunotherapy if their tumors were non-NE. Transcriptional phenotypes strongly skew towards the NE state in patient-derived model systems, an observation that was confirmed in paired patient-matched tumors and xenografts. We provide a framework that unifies transcriptomic and genomic dimensions of metastatic SCLC. The marked differences in transcriptional diversity between patient tumors and model systems are likely to have implications in development of novel therapeutic agents.

Notch signaling and efficacy of PD-1/PD-L1 blockade in relapsed small cell lung cancer.

Immune checkpoint blockade (ICB) benefits only a small subset of patients with small cell lung cancer (SCLC), yet the mechanisms driving benefit are poorly understood. To identify predictors of clinical benefit to ICB, we performed immunogenomic profiling of tumor samples from patients with relapsed SCLC. Tumors of patients who derive clinical benefit from ICB exhibit cytotoxic T-cell infiltration, high expression of antigen processing and presentation machinery (APM) genes, and low neuroendocrine (NE) differentiation. However, elevated Notch signaling, which positively correlates with low NE differentiation, most significantly predicts clinical benefit to ICB. Activation of Notch signaling in a NE human SCLC cell line induces a low NE phenotype, marked by increased expression of APM genes, demonstrating a mechanistic link between Notch activation, low NE differentiation and increased intrinsic tumor immunity. Our findings suggest Notch signaling as a determinant of response to ICB in SCLC.

Erratum: Anterior mediastinal large cell neuroendocrine carcinoma with elevated AFP: A case report and review.

[This corrects the article DOI: 10.3892/mco.2020.2196.].

Anterior mediastinal large cell neuroendocrine carcinoma with elevated AFP: A case report and review.

Large cell neuroendocrine carcinoma (LCNEC) is a rare and aggressive cancer that typically presents in the lung. The current case report describes a 56 year old male who presented to Strong Memorial Hospital with progressive dyspnea and was revealed to have a large anterior mediastinal tumor with metastases to axillary, hilar and mediastinal lymph nodes. Tumor marker results revealed an elevated plasma level of α-fetoprotein (AFP), which initially pointed towards a diagnosis of teratoma, but the tumor stained positive for neuroendocrine markers CD56, chromogranin, and synaptophysin on biopsy, consistent with LCNEC. AFP-positive tumor cells were identified, and no alternate cause for the elevated AFP was identified. The patient underwent genetic testing revealing the tumor to be ALK, ROS1, KRAS, BRAF and EGFR wild type. The patient received 6 cycles of chemotherapy with cisplatin (80 mg/m2) and etoposide (100 mg/m2) and then radiation with an initial minor response. The patients course was complicated by the development of superior vena cava syndrome requiring emergency stenting. The results of the current case suggest that AFP may be worthy of further exploration as a potential tumor marker in LCNEC.

Atorvastatin is associated with reduced cisplatin-induced hearing loss.

BACKGROUNDCisplatin is widely used to treat adult and pediatric cancers. It is the most ototoxic drug in clinical use, resulting in permanent hearing loss in approximately 50% of treated patients. There is a major need for therapies that prevent cisplatin-induced hearing loss. Studies in mice suggest that concurrent use of statins reduces cisplatin-induced hearing loss.METHODSWe examined hearing thresholds from 277 adults treated with cisplatin for head and neck cancer. Pretreatment and posttreatment audiograms were collected within 90 days of initiation and completion of cisplatin therapy. The primary outcome measure was a change in hearing as defined by the National Cancer Institute Common Terminology Criteria for Adverse Events (CTCAE).RESULTSAmong patients on concurrent atorvastatin, 9.7% experienced a CTCAE grade 2 or higher cisplatin-induced hearing loss compared with 29.4% in nonstatin users (P < 0.0001). A mixed-effect model analysis showed that atorvastatin use was significantly associated with reduced cisplatin-induced hearing loss (P ≤ 0.01). An adjusted odds ratio (OR) analysis indicated that an atorvastatin user is 53% less likely to acquire a cisplatin-induced hearing loss than a nonstatin user (OR = 0.47; 95% CI, 0.30-0.78). Three-year survival rates were not different between atorvastatin users and nonstatin users (P > 0.05).CONCLUSIONSOur data indicate that atorvastatin use is associated with reduced incidence and severity of cisplatin-induced hearing loss in adults being treated for head and neck cancer.TRIAL REGISTRATIONClinicalTrials.gov identifier NCT03225157.FUNDINGFunding was provided by the Division of Intramural Research at the National Institute on Deafness and Other Communication Disorders (1 ZIA DC000079, ZIA DC000090).

Risk of brain metastases in T1-3N0 NSCLC: a population-based analysis.

AIM: Several consensus guidelines recommend against routine brain imaging at diagnosis of T1-3N0 non-small cell lung cancer (NSCLC). METHODS: From the Surveillance, Epidemiology and End Results registry, patients with pathologically confirmed T1-3N0 NSCLC were identified. Risks of brain metastases at time of initial diagnosis were analyzed. RESULTS: Patients selected to not undergo primary NSCLC resection had approximately tenfold greater incidence of brain metastases versus those who did. Younger age, adenocarcinoma histology, higher tumor stage and higher histologic grade were all significantly (p < 0.0001) associated with greater likelihood of presenting with brain metastases. CONCLUSION: Given the morbidity and mortality of brain metastases, routine brain screening after NSCLC diagnosis (particularly adenocarcinoma) may be justifiable, though more refined cost-benefit analyses are warranted.

nab-Paclitaxel-Based Therapy in Underserved Patient Populations: The ABOUND.PS2 Study in Patients With NSCLC and a Performance Status of 2.

INTRODUCTION: The phase II ABOUND.PS2 study (NCT02289456) assessed safety/tolerability of a first-line modified nab-paclitaxel/carboplatin regimen for patients with advanced non-small cell lung cancer (NSCLC) and Eastern Cooperative Oncology Group (ECOG) performance status (PS) 2. METHODS: Chemotherapy-naive patients with stage IIIB/IV NSCLC and ECOG PS 2 received four cycles of nab-paclitaxel 100 mg/m2 days 1 and 8 plus carboplatin area under the curve 5 day 1 q3w (induction). Patients without progression received nab-paclitaxel monotherapy (100 mg/m2 days 1 and 8 q3w) until progression/unacceptable toxicity. Primary endpoint: percentage of patients discontinuing induction due to treatment-emergent adverse events (TEAEs). RESULTS: 11/40 treated patients (27.5%; 95% CI, 14.60-43.89) discontinued chemotherapy induction due to TEAEs; 16/40 (40.0%) continued nab-paclitaxel monotherapy. Median progression-free and overall survival were 4.4 (95% CI, 2.99-7.00) and 7.7 (95% CI, 4.93-13.17) months. Grade 3/4 TEAEs during induction included neutropenia (22.5%), anemia (17.5%), thrombocytopenia (5.0%), and peripheral neuropathy (2.5%). CONCLUSION: This nab-paclitaxel-based regimen was tolerable in patients with advanced NSCLC and ECOG PS 2, with efficacy comparable to historical chemotherapy data.

SWOG0919: a Phase 2 study of idarubicin and cytarabine in combination with pravastatin for relapsed acute myeloid leukaemia.

Inhibition of cholesterol synthesis and uptake sensitizes acute myeloid leukaemia (AML) blasts to chemotherapy. A Phase 1 study demonstrated the safety of high dose pravastatin given with idarubicin and cytarabine in patients with AML and also demonstrated an encouraging response rate. The Southwestern Oncology Group (SWOG) trial, SWOG S0919, was a Phase 2 trial evaluating the complete remission (CR) rate in a larger number of patients with relapsed AML treated with idarubicin, cytarabine and pravastatin. This study closed to accrual after meeting the defined criterion for a positive study. Thirty-six patients with a median age of 59 years (range 23-78) were enrolled. The median time from diagnosis to registration was 18 months. Relapse status was first relapse, 17 patients (47%); second relapse, 15 patients (42%); third relapse, two patients (5·5%) and fourth relapse, two patients (5·5%). The response rate was 75% [95% confidence interval: 58-88%; 20 CRs, 7 CR with incomplete count recovery (CRi)], and the median overall survival was 12 months. The P-value comparing 75-30% (the null response rate based on prior SWOG experience) was 3·356 × 10(-4) . Given the encouraging CR/CRi rate, this regimen should be considered for testing in a prospective randomized trial against best conventional therapy.

A phase I study of decitabine and rapamycin in relapsed/refractory AML.

A phase I study utilizing decitabine (DAC) followed by the mammalian target of rapamycin (mTOR) inhibitor, rapamycin, in patients with relapsed/refractory adult AML was undertaken to assess safety and feasibility. Patients received DAC 20mg/m(2) intravenously daily for 5 days followed by rapamycin from day 6 to day 25 at doses of 2 mg, 4 mg, and 6 mg/day in a standard 3+3 dose escalation design. Twelve patients completed treatment for safety evaluation. Maximum tolerated dose (MTD) was not reached, and except for grade 3 mucositis in 4 patients, no other significant unexpected non-hematologic toxicities have occurred indicating safety of this regimen. This trial is registered at clinical trials.gov as NCT00861874.

Phase 1 dose-ranging study of ezatiostat hydrochloride in combination with lenalidomide in patients with non-deletion (5q) low to intermediate-1 risk myelodysplastic syndrome (MDS).

BACKGROUND: Ezatiostat, a glutathione S-transferase P1-1 inhibitor, promotes the maturation of hematopoietic progenitors and induces apoptosis in cancer cells. RESULTS: Ezatiostat was administered to 19 patients with non-deletion(5q) myelodysplastic syndrome (MDS) at one of two doses (2000 mg or 2500 mg/day) in combination with 10 mg of lenalidomide on days 1-21 of a 28-day cycle. No unexpected toxicities occurred and the incidence and severity of adverse events (AEs) were consistent with that expected for each drug alone. The most common non-hematologic AEs related to ezatiostat in combination with lenalidomide were mostly grade 1 and 2 fatigue, anorexia, nausea, diarrhea, and vomiting; hematologic AEs due to lenalidomide were thrombocytopenia, neutropenia, and anemia. One of 4 evaluable patients (25%) in the 2500/10 mg dose group experienced an erythroid hematologic improvement (HI-E) response by 2006 MDS International Working Group (IWG) criteria. Four of 10 evaluable patients (40%) in the 2000 mg/10 mg dose group experienced an HI-E response. Three of 7 (43%) red blood cell (RBC) transfusion-dependent patients became RBC transfusion independent, including one patient for whom prior lenalidomide monotherapy was ineffective. Three of 5 (60%) thrombocytopenic patients had an HI-platelet (HI-P) response. Bilineage HI-E and HI-P responses occurred in 3 of 5 (60%), 1 of 3 with HI-E and HI-N (33%), and 1 of 3 with HI-N and HI-P (33%). One of 3 patients (33%) with pancytopenia experienced a complete trilineage response. All multilineage responses were observed in the 2000/10 mg doses recommended for future studies. CONCLUSIONS: The tolerability and activity profile of ezatiostat co-administered with lenalidomide supports the further development of ezatiostat in combination with lenalidomide in MDS and also encourages studies of this combination in other hematologic malignancies where lenalidomide is active.

A phase 2 randomized multicenter study of 2 extended dosing schedules of oral ezatiostat in low to intermediate-1 risk myelodysplastic syndrome.

BACKGROUND: Ezatiostat is a glutathione analog prodrug glutathione S-transferase P1-1 (GSTP1-1) inhibitor. This study evaluated 2 extended dose schedules of oral ezatiostat in 89 heavily pretreated patients with low to intermediate-1 risk myelodysplastic syndrome (MDS). METHODS: Patients were randomized by 1 stratification factor-baseline cytopenia (anemia only vs anemia with additional cytopenias)-to 1 of 2 extended dosing schedules. Multilineage hematologic improvement (HI) responses were assessed by International Working Group 2006 criteria. RESULTS: Overall, 11 of 38 (29%) red blood cell (RBC) transfusion-dependent patients had HI-Erythroid (HI-E) response. The median duration of HI-E response was 34 weeks. Multilineage responses were observed. There was 1 cytogenetic complete response in a del (5q) MDS patient. An important trend was the effect of prior therapy on response. A 40% HI-E rate (6 of 15 patients) was observed in patients who had prior lenalidomide and no prior hypomethylating agents (HMAs), with 5 of 11 (45%) patients achieving significant RBC transfusion reduction and 3 of 11 (27%) achieving transfusion independence. A 28% HI-E rate (5 of 18 patients) was observed in patients who were both lenalidomide and HMA naive, with 4 of 8 (50%) patients achieving clinically significant RBC transfusion reductions. Most common ezatiostat-related adverse events were grade 1 and 2 gastrointestinal including: nausea (45%, 17%), diarrhea (26%, 7%), and vomiting (30%, 12%). CONCLUSIONS: Ezatiostat is the first GSTP1-1 inhibitor shown to cause clinically significant and sustained reduction in RBC transfusions, transfusion independence, and multilineage responses in MDS patients. The tolerability and activity profile of ezatiostat may offer a new treatment option for patients with MDS.

Proteasome inhibition in myelodysplastic syndromes and acute myelogenous leukemia cell lines.

In this work, effects of bortezomib on apoptosis, clonal progenitor growth, cytokine production, and NF-κB expression in patients with MDS with cytopenias requiring transfusion support are examined. Bortezomib increased apoptosis in marrow mononuclear cells but had no effects on CFU-GM, BFU-E, or CFU-L content. No consistent effects on NF-κB activation in vivo were noted. To further define the role of bortezomib in AML and MDS, we examined it in combination with several targeted agents and chemotherapeutic agents in vitro. Combinations with arsenic trioxide, sorafenib, and cytarabine demonstrated synergistic in vitro effects in AML cell lines.

A phase 2 study of lenalidomide monotherapy in patients with deletion 5q acute myeloid leukemia: Southwest Oncology Group Study S0605.

Older acute myeloid leukemia (AML) patients with a chromosome 5q deletion have poor outcomes with conventional chemotherapy. This phase 2 study explored the safety and efficacy of single-agent lenalidomide in previously untreated older AML patients with del(5q) who declined standard chemotherapy. Patients were treated with lenalidomide 50 mg daily for 28 days as induction therapy and 10 mg daily for 21 days of a 28-day cycle as maintenance until disease progression or unacceptable toxicity. Among 37 evaluable patients, the median age was 74 years (range, 60-94), 21 (57%) were female, 19 (51%) had prior myelodysplastic syndrome, and 30 (81%) had pretreatment cytogenetic studies evaluated centrally. Six had isolated del(5q), 1 had del(5q) and +8, 23 had complex cytogenetics, and 7 others had del(5q) identified locally. Fourteen patients (38%) completed induction therapy: 7 patients died during induction therapy, 8 had disease progression, 7 had nonfatal adverse events, and 1 entered hospice. Eight patients started maintenance therapy. Five patients (14%) achieved a partial or complete response, 2 with isolated del(5q) and 3 with complex cytogenetics. Relapse-free survival was 5 months (range, 0-19). Median overall survival was 2 months for the entire population. In conclusion, lenalidomide as a single agent has modest activity in older del(5q) AML patients. Southwest Oncology Group Study S0605 is registered at www.clinicaltrials.gov as NCT00352365.

Sequential cytarabine and alpha-particle immunotherapy with bismuth-213-lintuzumab (HuM195) for acute myeloid leukemia.

PURPOSE: Lintuzumab (HuM195), a humanized anti-CD33 antibody, targets myeloid leukemia cells and has modest single-agent activity against acute myeloid leukemia (AML). To increase the potency of the antibody without the nonspecific cytotoxicity associated with ß-emitters, the α-particle-emitting radionuclide bismuth-213 ((213)Bi) was conjugated to lintuzumab. This phase I/II trial was conducted to determine the maximum tolerated dose (MTD) and antileukemic effects of (213)Bi-lintuzumab, the first targeted α-emitter, after partially cytoreductive chemotherapy. EXPERIMENTAL DESIGN: Thirty-one patients with newly diagnosed (n = 13) or relapsed/refractory (n = 18) AML (median age, 67 years; range, 37-80) were treated with cytarabine (200 mg/m(2)/d) for 5 days followed by (213)Bi-lintuzumab (18.5-46.25 MBq/kg). RESULTS: The MTD of (213)Bi-lintuzumab was 37 MB/kg; myelosuppression lasting >35 days was dose limiting. Extramedullary toxicities were primarily limited to grade ≤2 events, including infusion-related reactions. Transient grade 3/4 liver function abnormalities were seen in five patients (16%). Treatment-related deaths occurred in 2 of 21 (10%) patients who received the MTD. Significant reductions in marrow blasts were seen at all dose levels. The median response duration was 6 months (range, 2-12). Biodistribution and pharmacokinetic studies suggested that saturation of available CD33 sites by (213)Bi-lintuzumab was achieved after partial cytoreduction with cytarabine. CONCLUSIONS: Sequential administration of cytarabine and (213)Bi-lintuzumab is tolerable and can produce remissions in patients with AML.

Phase I study of cladribine, cytarabine (Ara-C), granulocyte colony stimulating factor (G-CSF) (CLAG Regimen) and simultaneous escalating doses of imatinib mesylate (Gleevec) in relapsed/refractory AML.

Receptor activated tyrosine kinases such as c-kit, c-fms and PDGFR are known targets of inhibition by imatinib mesylate (Gleevec) and are expressed on AML blasts. Marrow stromal cells and monocytes express KIT ligand, M-CSF and PDGF and are therefore capable of activating survival pathways in these leukemic cells. Given the synergy in vitro between Ara-C and imatinib mesylate on AML cell growth inhibition, we initiated a Phase I study combining CLAG+imatinib mesylate in AML patients. Patients with relapsed, refractory AML or CML myeloid blast crisis were eligible to receive Cladribine 5mg/m(2) days 3-7, Cytarabine 2gm/m(2) days 3-7, G-CSF 300mcg days 2-7, and escalating doses of imatinib mesylate given on days 1-15. The level 1 Gleevec dose was 400mg, while level 2 was 600mg and the level 3 dose 800mg. A total of 16 patients were enrolled, 15 AML and 1 CML myeloid blast crisis. The dose escalation occurred as planned and there was no clear evidence of added toxicity due to imatinib mesylate. One patient with an extensive cardiac history died of cardiac causes on day 1 of therapy however no other deaths occurred within 30 days of starting therapy. One patient had a Grade 3 skin rash at dose level 2. The most common toxicities encountered during induction therapy were nausea, vomiting, rash and diarrhea that were transient and/or reversible. At the 800mg dose 1 patient developed a decline in cardiac ejection fraction on day 20 who later died of sepsis, so this was considered a dose limiting toxicity. Of 16 evaluable patients 11 achieved a hypocellular marrow after initial induction with 1 additional patient achieving a hypocellular marrow following a second course of the same regimen. Four patients (25%) achieved a complete morphologic response with normal cytogenetics, 2 patients (12.5%) achieved a complete morphologic response only and 1 patient had a complete response in the bone marrow but incomplete blood count recovery. The overall response rate was 43.8%. The median overall survival was 175 days (95% CI 16.24-333.76) and the median relapse free survival was 76 days. The addition of imatinib mesylate to CLAG was well tolerated with acceptable toxicities and response rates comparable to other salvage regimens. To assess the efficacy of imatinib mesylate in combination with CLAG, a larger phase II trial is now planned.

Rapid method for detection of mutations in the nucleophosmin gene in acute myeloid leukemia.

Mutations in exon 12 of the nucleophosmin gene (NPM1) that cause the encoded protein to abnormally relocate to the cytoplasm are found at diagnosis in about 50% of karyotypically normal acute myeloid leukemias and are associated with a more favorable outcome. We have devised a PCR-based assay for NPM1 exon 12 mutations using differential melting of an oligo probe labeled with a fluorescent dye. The nucleobase quenching (NBQ) phenomenon was used to detect probe hybridization, and an oligonucleotide containing locked nucleic acid (LNA) nucleotides was used as a PCR clamp to suppress amplification of the normal sequence and enhance the analytical sensitivity of the assay. After the NBQ assay, the specimens with a mutation were removed from the capillary and sequenced to identify the mutation. The use of the LNA clamp facilitates interpretation of the mutant sequence because of the lower intensity of the overlapping normal sequence. Analysis of a series of 70 patient specimens revealed 17 positive for an NPM1 mutation and 53 negatives. All of the NBQ results (positives and negatives) were confirmed with other methods. The analytical sensitivity of the NBQ assay is variable depending on the concentration of the PCR clamp and other parameters. Using a 100 nmol/L concentration of the LNA clamp, NPM1 mutations were detectable in a 10-fold excess of wild-type DNA. This assay may be valuable for screening disease specimens.

Antibody therapy for acute myeloid leukemia.

Due to the high rate of relapse in younger patients and the overall poor outcome in older patients, novel therapies are needed for the treatment of acute myeloid leukemia (AML). Monoclonal antibodies have become an important treatment modality in cancer therapy. Gemtuzumab ozogamicin (GO), an anti-CD33 immunoconjugate, was approved by the US Food and Drug Administration (FDA) for the treatment of elderly patients with relapsed AML who are not candidates for standard chemotherapy. Single-agent GO and combinations with standard chemotherapeutics have been explored extensively in this disease. Hepatotoxicity and delayed myelosuppression have been dose-limiting. Its toxicity profile is reduced with decreased doses of GO and even by administering only a single infusion. In patients with acute promyelocytic leukemia (APL), the addition of GO can produce molecular remissions and is well tolerated. Targeted immunotherapy with GO for treatment of AML has produced remissions. In order to reduce toxicity and improve efficacy, its optimal dose and schedule and pairing with other standard chemotherapeutic agents need to be defined better in large clinical trials.

The promise of targeted {alpha}-particle therapy.

The use of monoclonal antibodies to deliver radioisotopes directly to tumor cells has become a promising strategy to enhance the antitumor effects of native antibodies. Since the alpha- and beta-particles emitted during the decay of radioisotopes differ in significant ways, proper selection of isotope and antibody combinations is crucial to making radioimmunotherapy a standard therapeutic modality. Because of the short pathlength (50-80 microm) and high linear energy transfer ( approximately 100 keV/microm) of alpha-emitting radioisotopes, targeted alpha-particle therapy offers the potential for more specific tumor cell killing with less damage to surrounding normal tissues than beta-emitters. These properties make targeted alpha-particle therapy ideal for the elimination of minimal residual or micrometastatic disease. Radioimmunotherapy using alpha-emitters such as (213)Bi, (211)At, and (225)Ac has shown activity in several in vitro and in vivo experimental models. Clinical trials have demonstrated the safety, feasibility, and activity of targeted alpha-particle therapy in the treatment of small-volume and cytoreduced disease. Further advances will require investigation of more potent isotopes, new sources and methods of isotope production, improved chelation techniques, better methods for pharmacokinetic and dosimetric modeling, and new methods of isotope delivery such as pretargeting. Treatment of patients with less-advanced disease and, ultimately, randomized trials comparing targeted alpha-particle therapy with standard approaches will be required to determine the clinical utility of this approach.