Maximizing the value of phase III trials in immuno-oncology: A checklist from the Society for Immunotherapy of Cancer (SITC)

The broad activity of agents blocking the programmed cell death protein 1 and its ligand (the PD-(L)1 axis) revolutionized oncology, offering long-term benefit to patients and even curative responses for tumors that were once associated with dismal prognosis. However, only a minority of patients experience durable clinical benefit with immune checkpoint inhibitor monotherapy in most disease settings. Spurred by preclinical and correlative studies to understand mechanisms of non-response to the PD-(L)1 antagonists and by combination studies in animal tumor models, many drug development programs were designed to combine anti-PD-(L)1 with a variety of approved and investigational chemotherapies, tumor-targeted therapies, antiangiogenic therapies, and other immunotherapies. Several immunotherapy combinations improved survival outcomes in a variety of indications including melanoma, lung, kidney, and liver cancer, among others. This immunotherapy renaissance, however, has led to many combinations being advanced to late-stage development without definitive predictive biomarkers, limited phase I and phase II data, or clinical trial designs that are not optimized for demonstrating the unique attributes of immune-related antitumor activity-for example, landmark progression-free survival and overall survival. The decision to activate a study at an individual site is investigator-driven, and generalized frameworks to evaluate the potential for phase III trials in immuno-oncology to yield positive data, particularly to increase the number of curative responses or otherwise advance the field have thus far been lacking. To assist in evaluating the potential value to patients and the immunotherapy field of phase III trials, the Society for Immunotherapy of Cancer (SITC) has developed a checklist for investigators, described in this manuscript. Although the checklist focuses on anti-PD-(L)1-based combinations, it may be applied to any regimen in which immune modulation is an important component of the antitumor effect.

Clinical pharmacokinetics of bdtx-189, an inhibitor of allosteric ErbB mutations, in patients with advanced solid malignancies in MasterKey-01 study

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Background: Allosteric oncogenic mutations occur outside the canonical ATP-binding site of EGFR and HER2, and there are no approved therapies that target such mutations. BDTX-189 is a potent, selective, irreversible inhibitor of 48 allosteric EGFR and HER2 mutant variants under clinical evaluation in the ongoing MasterKey-01 trial (NCT04209465). BDTX-189 was designed to rapidly and irreversibly occupy the active site of targeted ErbB mutants, leading to sustained pharmacodynamic (PD) effects, and with selectivity over EGFR-WT in order to minimize EGFR-WT mediated toxicities. The pharmacokinetic (PK) profile was designed for rapid absorption and fast elimination to maintain target occupancy while minimizing prolonged drug exposure that could contribute to off-target associated toxicities. Methods: In MasterKey-01, BDTX-189 was administered orally once daily in continuous 21-day cycles, taken fasted. Dose escalation included cohorts of 1-2 patients receiving doses between 25 and 200 mg QD followed by 5-7 patients receiving 400 mg, 800 mg, or 1,200 mg QD fasted. The possible effects of a high fat meal on the PK of BDTX-189 were assessed in a subset of patients receiving single doses of 400 mg BDTX-189 fasted and immediately after a high-fat breakfast in a randomized crossover fashion with 3 days between doses. In addition, a dose escalation cohort investigating administration of BDTX-189 non-fasted was enrolled at 800 mg QD. Serial blood samples for analysis of plasma BDTX-189 concentrations were collected after each dose on C1D1 and C1D15. BDTX-189 levels were determined using LC-MS, and data analyzed using non-compartmental methods. Results: After single and multiple doses, BDTX-189 was rapidly absorbed (median tmax 1-2 h), with an elimination t1/2 of 2-6 h. Dose-dependent increases in exposure from 200 to 800 mg QD fasted were observed, with no apparent accumulation or decline in exposures observed at steady-state. Administration of BDTX-189 with a high-fat meal increased AUC approximately 1.7-fold with minimal effect on Cmax, relative to administration in the fasted state. At 800 mg QD, mean AUC was similar in the non-fasting state relative to fasting and was within the target efficacious range defined by mouse models harboring allo-ErbB mutated tumors. Median tmax and t1/2 values were similar after administration in the non-fasted and fasted states. Conclusions: BDTX-189 demonstrated rapid absorption and a short PK half-life consistent with the desired PK/PD profile, with exposures in the efficacious target range based on preclinical data. The pilot high fat food-effect data and non-fasting QD dosing regimen show similar or improved systemic exposure relative to dosing in the fasted state. The MasterKey-01 trial is ongoing, including refinement of the dosing regimen and identification of the recommended phase 2 dose. Clinical trial information: NCT04209465.

Safety and preliminary efficacy from the phase 1 portion of MasterKey-01: A First-in-human dose-escalation study to determine the recommended phase 2 dose (RP2D), pharmacokinetics (PK) and preliminary antitumor activity of BDTX-189, an inhibitor of allosteric ErbB mutations, in patients (pts) with advanced solid malignancies

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Background: BDTX-189 is an orally available, ATP-competitive and irreversible inhibitor directed against families of allosteric HER2 and EGFR oncogenic mutations. In preclinical studies BDTX-189 achieved potent inhibition of 48 allosteric HER2 and EGFR/HER2 exon 20 insertion mutant variants with selectivity versus EGFR wild-type (WT) and demonstrated tumor growth inhibition and regression in vivo. The primary objective of the Ph 1 portion of this trial (NCT04209465) is to determine the RP2D and schedule of monotherapy BDTX-189 in pts with advanced solid tumors. Methods: Eligibility includes pts with relapsed or refractory locally advanced or metastatic solid tumors with no standard therapy available whose tumor harbors an allosteric HER2 or HER3 mutation; EGFR or HER2 exon 20 insertion mutation; HER2 amplification or overexpression; or EGFR exon 19 deletion or L858R mutation. BDTX-189 is dosed continuously orally in 3-wk cycles QD and BID in separate dose escalation cohorts. A separate cohort is also evaluating the high- and low-fat food-effect (FE) on BDTX-189 PK. Results: As of 1/11/21, 46 pts have been dosed, with 36 in the QD (fasting) schedule (25-1200 mg), including pts from the FE cohort who received 800 mg QD fasting after FE evaluation: 58% female; 67% white; median age 63.5 yrs; 53% received ≥ 3 prior tx lines. Cancer types: 12 NSCLC, 5 breast, 4 ovary, 3 biliary, and 12 other. Genomic alterations: 23 HER2 amplification and the following mutations: 11 allosteric HER2, 5 EGFR exon 20 insertion, 5 HER2 exon 20 insertion, 3 EGFR exon 19 del./L858R, and 2 HER3. At ≥ 800 mg QD, 3 and 2 pts had EGFR or HER2 exon 20 mutations, respectively. The maximum tolerated dose (MTD) for QD (fasting) was 800 mg, with 2/6 pts with DLTs at 1200 mg. DLTs: gastrointestinal (G3 diarrhea; G1/2 nausea/vomiting). The most frequent (≥20%) related adverse events were diarrhea (36%, 8% G3), nausea (28%, 0% G3), and vomiting (25%, 3% G3). The rate of skin disorders was 11% with the highest severity of G2 in 1 pt. Dose-dependent exposure increases were observed, with the exposure at 800 mg QD fasting within the projected efficacious range. Pilot FE data suggest possible increased exposure with food. 27 pts were evaluable for efficacy, 15 at ≥ 800 mg QD, with 2 partial responses observed: 1 PR confirmed and ongoing (800 mg QD, CUP, HER2 amp, 3 prior lines of chemo) and 1 PR unconfirmed (NSCLC with brain mets, 1200 mg QD, HER2 amp + exon 19 del., 2 prior EGFR TKIs). 3 pts had a best response of SD and 10 with progressive disease. Conclusions: BDTX-189 has a generally manageable safety profile with early evidence of anti-tumor activity. Enrollment is ongoing in non-fasting QD and BID cohorts, and the FE cohort, prior to RP2D identification. Clinical trial information: NCT04209465.

Defining tumor resistance to PD-1 pathway blockade: recommendations from the first meeting of the SITC Immunotherapy Resistance Taskforce

As the field of cancer immunotherapy continues to advance at a fast pace, treatment approaches and drug development are evolving rapidly to maximize patient benefit. New agents are commonly evaluated for activity in patients who had previously received a programmed death receptor 1 (PD-1)/programmed death-ligand 1 (PD-L1) inhibitor as standard of care or in an investigational study. However, because of the kinetics and patterns of response to PD-1/PD-L1 blockade, and the lack of consistency in the clinical definitions of resistance to therapy, the design of clinical trials of new agents and interpretation of results remains an important challenge. To address this unmet need, the Society for Immunotherapy of Cancer convened a multistakeholder taskforce-consisting of experts in cancer immunotherapy from academia, industry, and government-to generate consensus clinical definitions for resistance to PD-(L)1 inhibitors in three distinct scenarios: primary resistance, secondary resistance, and progression after treatment discontinuation. The taskforce generated consensus on several key issues such as the timeframes that delineate each type of resistance, the necessity for confirmatory scans, and identified caveats for each specific resistance classification. The goal of this effort is to provide guidance for clinical trial design and to support analyses of emerging molecular and cellular data surrounding mechanisms of resistance.

Probody Therapeutics: An Emerging Class of Therapies Designed to Enhance On-Target Effects with Reduced Off-Tumor Toxicity for Use in Immuno-Oncology

The deep and durable antitumor effects of antibody-based immunotherapies such as immune checkpoint inhibitors (ICIs) have revolutionized oncology and transformed the therapeutic landscape for many cancers. Several anti-programmed death receptor 1 and anti-programmed death receptor ligand 1 antibodies have been approved for use in advanced solid tumors, including melanoma, non-small cell lung cancer, bladder cancer, and other cancers. ICIs are under development across many tumor types and preliminary results are compelling. However, ICIs have been associated with severe immune-related adverse events (irAEs), including rash, diarrhea, colitis, hypophysitis, hepatotoxicity, and hypothyroidism, which in some cases lead to high morbidity, are potentially life-threatening, and limit the duration of treatment. The incidence of severe irAEs increases further when programmed cell death-1 and programmed cell death ligand-1 inhibitors are combined with anti-CTLA-4 and/or other multidrug regimens. Probody therapeutics, a new class of recombinant, proteolytically activated antibody prodrugs are in early development and are designed to exploit the hallmark of dysregulation of tumor protease activity to deliver their therapeutic effects within the tumor microenvironment (TME) rather than peripheral tissue. TME targeting, rather than systemic targeting, may reduce irAEs in tissues distant from the tumor. Probody therapeutic technology has been applied to multiple antibody formats, including immunotherapies, Probody drug conjugates, and T-cell-redirecting bispecific Probody therapeutics. In preclinical models, Probody therapeutics have consistently maintained anticancer activity with improved safety in animals compared with the non-Probody parent antibody. In the clinical setting, Probody therapeutics may expand or create therapeutic windows for anticancer therapies.

PROCLAIM-001: A first-in-human trial to assess tolerability of the protease-activatable anti-PD-L1 Probody CX-072 in solid tumors and lymphomas

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Background: CX-072 is a novel Probody™ therapeutic (PbTx) targeting PD-L1. PbTx’s are fully recombinant antibody prodrugs designed to be converted to active antibodies by tumor-associated proteases that are highly expressed malignant tissue; the PbTx remains largely inactive in normal tissues. In pre-clinical tumor models, a PD-L1-directed PbTx provided comparable anti-tumor efficacy to its parental anti-PD-L1 antibody, but displayed reduced auto-immunity in a model of Type 1 diabetes. Based on these pre-clinical data, CX-072 has the potential to enable combination therapies that are otherwise poorly tolerated. This Phase 1/2 study (PROCLAIM-001 (PRObody CLinical Assessment In Man) assesses the tolerability and antitumor activity of CX-072 in humans with an emphasis on immune-related adverse events, particularly in combinations. CX-072 will be administered as monotherapy (Part A), in combination with 2 schedules of ipilimumab (Parts B1 and B2) and in combination with vemurafenib (Part C). The expansion cohort (Part D) will include CX-072 monotherapy in PD-L1 responsive tumor types. Methods: Key eligibility criteria are as follows: Parts A and B1: checkpoint inhibitor-naive patients with advanced, refractory solid tumor or lymphoma (unmeasurable disease allowed) for whom approved PD agents are not available. Part B2: advanced, refractory solid tumors or lymphomas with measurable disease who have progressed on a previous treatment with a PD-(L)1 inhibitor, but did not discontinue due to toxicity. Part C: checkpoint inhibitor, BRAF-inhibitor and MEK-inhibitor-naïve metastatic V600E BRAF-mutated melanoma. Patients without an active autoimmune disease, ongoing infection, and ECOG PS 0-1 may be eligible to participate in the study. Dose escalation follows the 3+3 design in all arms. Ipilimumab (Parts B1 and B2) is dosed at the approved 3 mg/kg every 3 weeks x 4. The dose of vemurafenib (Part C) is 960 mg/kg twice daily. Exploratory biomarkers are used to characterize tumor protease activity, inflammatory changes within the tumor, and CX-072 activation in tumor versus peripheral blood. Clinical trial information: NCT03013491.

Opportunities and challenges in the development of experimental drug combinations for cancer

It is becoming increasingly evident that cancers are dependent on a number of altered molecular pathways and can develop diverse mechanisms of resistance to therapy with single agents. Therefore, combination regimens may provide the best hope for effective therapies with durable effects. Despite preclinical data to support this notion, there are many challenges to the development of targeted combinations including scientific, economic, legal, and regulatory barriers. A discussion of these challenges and identification of models and best practices are presented with intent of aiding the research community in addressing real and perceived barriers to the development of combination therapies for cancer.

A phase I trial of the pharmacokinetics, toxicity, and activity of KNI-272, an inhibitor of HIV-1 protease, in patients with AIDS or symptomatic HIV infection

The pharmacokinetics, toxicity, and activity of KNI-272, a transition state inhibitor of HIV-1 protease, was assessed in a phase I trial. After an initial phase in which the pharmacokinetics were assessed, 37 patients with AIDS or symptomatic HIV infection and 100-400 CD4 cells/mm3 were entered in an escalating dose study. KNI-272 was administered four times daily for up to 12 weeks. Oral bioavailability ranged from 22 to 55% and was not appreciably different in the fasting and post-prandial state. The dose limiting toxicity was hepatic transaminase elevation; this could be reduced by escalating the dose over 4 weeks. When administered this way, the maximum tolerated oral dose was 40 mg/kg per day. At the highest two tolerated doses (26.4 and 40 mg/kg per day), there was some evidence of an anti-HIV effect with median decreases of 0.2-0.3 log10 copies/ml plasma HIV RNA; these decreases persisted through 7-8 weeks of treatment. There was an upward trend in the CD4 count at the 40 mg/kg per day dose but not at other doses. Additional studies focused on approaches to improve the therapeutic index of KNI-272 may be warranted.

Relative potency of protease inhibitors in monocytes/macrophages acutely and chronically infected with human immunodeficiency virus

The activity of three human immunodeficiency virus (HIV) protease inhibitors was investigated in human primary monocytes/macrophages (M/M) chronically infected by HIV-1. Saquinavir, KNI-272, and ritonavir inhibited the replication of HIV-1 in vitro, with EC50s of approximately 0.5-3.3 microM. However, only partial inhibition was achievable, even at the highest concentrations tested. Also, the activity of these drugs in chronically infected M/M was approximately 7- to 26-fold lower than in acutely infected M/M and approximately 2- to 10-fold lower than in chronically infected H9 lymphocytes. When protease inhibitors were removed from cultures of chronically infected M/M, production of virus rapidly returned to the levels found in untreated M/M. Therefore, relatively high concentrations of protease inhibitors are required to suppress HIV-1 production in chronically infected macrophages, and such cells may be a vulnerable point for the escape of virus in patients taking these drugs.

Phase II trial with dose titration of paclitaxel for the therapy of human immunodeficiency virus-associated Kaposi's sarcoma

PURPOSE

To investigate the antitumor activity and safety of paclitaxel in patients with advanced human immunodeficiency virus (HIV)-associated Kaposi's sarcoma (KS).

PATIENTS AND METHODS

Twenty-nine patients with advanced HIV-associated KS were enrolled. The patients were overall quite immunosuppressed (median CD4 count, 15 cells/microL). Paclitaxel was initially administered at 135 mg/m2 over 3 hours every 3 weeks without filgrastim support; the dose was increased as tolerated to a maximum of 175 mg/m2. Patients who failed to respond or progressed could then receive filgrastim support or paclitaxel administered over 96 hours.

RESULTS

Of 28 assessable patients, 20 had major responses (18 partial responses [PRs], one clinical complete response [CR], and one CR), for a major response rate of 71.4% (95% confidence interval [CI], 51.3% to 86.8%). Each of the five patients with pulmonary KS responded, as did all four assessable patients who had previously received anthracycline therapy for KS. Of six patients who went on to receive a 96-hour infusion of paclitaxel, five had major responses. Neutropenia was the most frequent dose-limiting toxicity; possible novel toxicities included late fevers, late rash, and eosinophilia. Two patients developed an elevated creatinine concentration and one cardiomyopathy.

CONCLUSION

Paclitaxel has substantial activity against advanced HIV-associated KS as a single agent, even in patients with pulmonary involvement or who had previously received anthracyclines. Further research is needed to define the optimal treatment schedule and its role vis-a-vis the other available therapies for this disease.

Human herpesvirus 8 (HHV-8) in the pathogenesis of Kaposi's sarcoma and other diseases

The discovery of Kaposi's Sarcoma-associated herpesvirus/human herpesvirus-8 (KSHV/ HHV-8) and subsequent studies of this virus have provided a body of evidence that support the concept that this is an etiologic agent for Kaposi's sarcoma (KS). Several studies have indicated that this virus may also be a causal agent for primary effusion lymphoma (PEL) and Castleman's disease as well. First generation serologic assays for HHV-8 have now been developed. The preponderance of data suggest that the incidence of HHV-8 infection is highest in populations at risk for KS: male homosexuals, immunosuppressed patients, and those who live in endemic regions. HHV-8 encodes for functional homologs of human proteins that may play a role in the development of disease. As we learn more about the steps by which this virus can lead to KS and/or other diseases, rational therapies and preventative strategies may be possible.

Removal of human immunodeficiency virus type 1 (HIV-1) protease inhibitors from preparations of immature HIV-1 virions does not result in an increase in infectivity or the appearance of mature morphology

The processing of gag and gag-pol polyproteins by human immunodeficiency virus type 1 (HIV-1) protease is a crucial step in the formation of infectious HIV-1 virions. In this study, we examine whether particles produced in the presence of inhibitors of HIV-1 protease can subsequently undergo gag polyprotein cleavage with restoration of infectivity following removal of the inhibitors. Viral particles produced during 7 days of culture in the presence of the protease inhibitors KNI-272 (10 microM) and saquinavir (5 microM) contained predominantly p55gag polyprotein but little or no p24gag cleavage product. Following resuspension of the particles in medium free of the inhibitor, some gag polyprotein processing was detected in particles produced from the KNI-272-treated cells, but not from the saquinavir-treated cells within the first 3 h. However, the majority of the protein remained as p55gag throughout a 48-h experimental period. The infectivity (50% tissue culture infective dose per milliliter) of the viral particles from KNI-272-treated cells was 10(6)-fold lower than that of control particles and did not significantly increase over the 48 h after the inhibitor was removed, despite the apparent return of protease function in a subset of these virions. This failure to restore infectivity was due neither to a reduction in the number of particles produced by protease inhibitor-treated cells nor to a failure of HIV RNA to be packaged in the virions. These particles also failed to express the mature phenotype by electron microscopy. Thus, while some processing of the gag polyprotein can occur in isolated HIV virions, this does not appear to be sufficient to restore infectivity in the majority of particles. This finding suggests that there may be constraints on postbudding polyprotein processing in the production of viable particles. These results should have positive implications regarding the use of protease inhibitors as anti-HIV drugs.

Detection of serum antibodies to a Kaposi's sarcoma-associated herpesvirus-specific peptide

Kaposi's sarcoma (KS)-associated herpesvirus/human herpesvirus type 8 (KSHV/HHV-8) may play an etiologic role in the pathogenesis of KS. In an attempt to assess KSHV/HHV-8 infection, an ELISA was developed using an 18-amino acid peptide from a putative minor capsid protein of KSHV/HHV-8 conjugated to bovine serum albumin. Overall, sera from human immunodeficiency virus type 1 (HIV-1)-positive patients with KS had a higher reactivity in the assay than did sera from HIV-1-positive patients without KS (P = .018). Of 35 HIV-1-positive patients with KS, 60% were antibody positive, compared with 27% of 33 HIV-1-positive patients without KS. Of 30 healthy blood donors, 20% were antibody positive. The ELISA responses did not correlate with antibody titers to Epstein-Barr virus. Given the homology and antigenic relatedness between KSHV/HHV-8 and Epstein-Barr virus, serologic assays involving unique KSHV/HHV-8 peptides may prove to be valuable in defining the epidemiology and clinical expression of this virus.

Kaposi's sarcoma (KS)-associated herpesvirus-like DNA sequences in peripheral blood mononuclear cells: association with KS and persistence in patients receiving anti-herpesvirus drugs

Herpesvirus-like DNA sequences (KSHV/HHV-8) have recently been described in AIDS-associated Kaposi's sarcoma (KS) lesions. Many questions remain regarding the role of this virus in KS and the therapeutic implications of this finding. In the current study, KSHV/HHV-8 DNA was detected in peripheral blood mononuclear cells (PBMCs) from human immunodeficiency virus (HIV)-infected patients with KS (34/98) more often than in HIV-infected individuals without KS (12/64, P = .03). The detection of KSHV/HHV-8 DNA did not correlate with the CD4 lymphocyte count. Five patients demonstrated KSHV/HHV-8 DNA in their PBMCs during administration of intravenous foscarnet and/or ganciclovir. The continued detection of KSHV/HHV-8 DNA in the PBMCs of patients receiving these anti-herpesvirus drugs has potential implications regarding the virus-cell relationship of KSHV/HHV-8, as well as for the value of these drugs in treating or preventing KS, but additional studies are needed.

Inhibition of the human immunodeficiency virus-1 protease and human immunodeficiency virus-1 replication by bathocuproine disulfonic acid Cu1+

The protease encoded by the human immunodeficiency virus-1 (HIV-1) is essential for processing viral polyproteins which contain the enzymes and structural proteins required for the infectious virus. It was previously found that cupric chloride, in the presence of dithiothreitol or ascorbic acid, could inhibit the HIV-1 protease. It was suggested that a Cu1+ chelate was the moiety responsible for inhibition of the protease. This hypothesis has now been investigated directly by utilizing the stable Cu1+ chelate, bathocuproine disulfonic acid Cu1+ (BCDS-Cu1+). BCDS-Cu1+ inhibited the HIV-1 wild type protease as well as a mutant HIV-1 protease lacking cysteines. BCDS-Cu1+ was a competitive inhibitor of the mutant HIV-1 protease with an apparent Ki of 1 microM. Replication of HIV-1 in human lymphocytes and the cytotoxic effect of HIV-1 in CEM cells was inhibited by micromolar BCDS-Cu1+. Inhibition of the protease and of HIV replication by BCDS-Cu1+ was dependent on the presence of Cu1+ as BCDS alone was ineffective. EDTA blocked the inhibition of the protease by Cu1+ but was unable to block inhibition of the protease by BCDS-Cu1+, indicating that the Cu1+ complex was the inhibitory agent. The apparent IC50 for BCDS-Cu1+ on the inhibition of replication by primary isolates of HIV-1 was 5 microM. However, BCDS-Cu1+ did not affect polyprotein processing in an H9 cell line chronically infected with HIV-1, indicating that BCDS-Cu1+ acts by yet another mechanism to block HIV infection. Other possible targets for BCDS-Cu1+ include inhibition of viral adsorption and/or inhibition of the HIV-1 integrase.

Treatment of HIV-associated Kaposi's sarcoma with paclitaxel

We investigated whether paclitaxel was active in AIDS-associated Kaposi's sarcoma. We gave 135 mg/m2 intravenously over 3 hours every 21 days. Follow-up is available on the first 20 patients, most of whom had advanced Kaposi's sarcoma and severe immunocompromise. Neutropenia was the most frequent dose-limiting toxic effect; novel toxic effects included late fevers, rash, and eosinophilia. Creatinine increased in 2 patients and 1 patient had cardiomyopathy. There were 13 partial responses (65%, 95% CI 41-85%). All 5 patients with pulmonary involvement responded. Paclitaxel appears to be active against Kaposi's sarcoma as a single agent. Further studies, including a randomised trial, are warranted.

Identification and characterization of nonsedimentable lipid-protein microvesicles

Previously uncharacterized lipid-protein microvesicles have been isolated from young and senescing bean cotyledon tissue. The microvesicles are nonsedimentable and enriched in phospholipid degradation products (free fatty acids, long-chain aldehydes, and long-chain hydrocarbons). They range from 70 to 170 nm (radius) with a mean radius of 132 nm, and it is clear from freeze-fracture electron micrographs that they are bilayered in nature. Nonsedimentable lipid-protein microvesicles containing the same products of phospholipid degradation but smaller were also formed in vitro when smooth microsomal membranes from young cotyledon tissue were treated with Ca2+ to stimulate enzymatic degradation of phospholipids. The data suggest that these microvesicles comprise an intermediate stage of membrane lipid deterioration. They appear to serve as a vehicle for moving phospholipid degradation products out of membranes into the cytosol during senescence and perhaps also during normal membrane lipid turnover.

Mitochondrial and myocardial performance. Response to ischemia and reperfusion

The relationships between cardiac bioenergy metabolism and myocardial function were examined in a model of global myocardial ischemia and reperfusion. The respiratory activity of distinct populations of subsarcolemmal and interfibrillar mitochondria was correlated with max dP/dt (an index of myocardial contractility with respect to time). Max dP/dt was significantly reduced to 27% of the preischemic value following two hours of cardioplegia-protected, warm, global, ischemia in dogs during the cardiopulmonary bypass period. Reperfusion resulted in improved myocardial function such that by 60 minutes of reperfusion, max dP/dt returned to baseline. Significant declines in both state 3 respiratory rates and respiratory control indexes for subsarcolemmal and interfibrillar mitochondria were noted following the ischemic interval. Mitochondrial function similarly returned to baseline values following 60 minutes of reperfusion. These data demonstrate a close association between mitochondrial and myocardial activity.

Ruptured mycotic salmonella aortic aneurysm treated with combined cefotaxime antibiotic and staged surgical management

A case of salmonella infrarenal aortic aneurysm that ruptured and was treated with staged operative procedures and a highly effective antibiotic is reported and analyzed. An emergency situation with a ruptured abdominal aortic aneurysm required prompt surgical intervention with an aortobifemoral graft insertion. In the immediate postoperative period it was realized that a prosthetic graft was placed in the bed of a mycotic aneurysm. The patient had significant arteriosclerotic occlusive disease limiting the distal anastomotic site to the common femorals. Interoperatively the superficial femorals were noted to be occluded chronically. Consequently, revascularization via an extra-anatomical bypass after aortobifemoral graft removal was more complex. This was managed in a staged delayed fashion, while suppressing the infecting organism with Cefotaxime. The details of this complex situation are described within.