Clinical Pharmacology and Translational Considerations in the Development of CRISPR-Based Therapies

Genome editing holds the potential for curative treatments of human disease, however, clinical realization has proven to be a challenging journey with incremental progress made up until recently. Over the last decade, advances in clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein (Cas) systems have provided the necessary breakthrough for genome editing in the clinic. The progress of investigational CRISPR therapies from bench to bedside reflects the culmination of multiple advances occurring in parallel, several of which intersect with clinical pharmacology and translation. Directing the CRISPR therapy to the intended site of action has necessitated novel delivery platforms, and this has resulted in special considerations for the complete characterization of distribution, metabolism, and excretion, as well as immunogenicity. Once at the site of action, CRISPR therapies aim to make permanent alterations to the genome and achieve therapeutically relevant effects with a single dose. This fundamental aspect of the mechanism of action for CRISPR therapies results in new considerations for clinical translation and dose selection. Early advances in model-informed development of CRISPR therapies have incorporated key facets of the mechanism of action and have captured hallmark features of clinical pharmacokinetics and pharmacodynamics from phase I investigations. Given the recent emergence of CRISPR therapies in clinical development, the landscape continues to evolve rapidly with ample opportunity for continued innovation. Here, we provide a snapshot of selected topics in clinical pharmacology and translation that has supported the advance of systemically administered in vivo and ex vivo CRISPR-based investigational therapies in the clinic.

Phase I, First-in-Human Study of the Probody Therapeutic CX-2029 in Adults with Advanced Solid Tumor Malignancies

PURPOSE

PROCLAIM-CX-2029 is a phase I first-in-human study of CX-2029, a Probody-drug conjugate targeting CD71 (transferrin receptor 1) in adults with advanced solid tumors. Although the transferrin receptor is highly expressed across multiple tumor types, it has not been considered a target for antibody-drug conjugates (ADCs) due to its broad expression on normal cells. CX-2029 is a masked form of a proprietary anti-CD71 antibody conjugated to monomethyl auristatin E, designed to be unmasked in the tumor microenvironment by tumor-associated proteases, therefore limiting off-tumor toxicity and creating a therapeutic window for this previously undruggable target.

PATIENTS AND METHODS

This was a dose-escalation, multicenter trial to evaluate the safety, pharmacokinetics, pharmacodynamics, and antitumor activity of CX-2029. The primary endpoint was to determine the maximum tolerated dose (MTD) and cycle 1 dose-limiting toxicity (DLT). CX-2029 was administered i.v. every 3 weeks.

RESULTS

Forty-five patients were enrolled in eight dose levels. No DLTs were reported in the dose escalation through 4 mg/kg. At 5 mg/kg, there were two DLTs (febrile neutropenia and pancytopenia). Following expansion of the 4 mg/kg dose to six patients, two additional DLTs were observed (infusion-related reaction and neutropenia/anemia). Both the 4 and 5 mg/kg doses were declared above the maximum tolerated dose. The recommended phase II dose is 3 mg/kg. The most common dose-dependent hematologic toxicities were anemia and neutropenia. Confirmed partial responses were observed in three patients, all with squamous histologies.

CONCLUSIONS

The Probody therapeutic platform enables targeting CD71, a previously undruggable ADC target, at tolerable doses associated with clinical activity.See related commentary by Oberoi and Garralda, p. 4459.

CX-072 (pacmilimab), a Probody PD-L1 inhibitor, in combination with ipilimumab in patients with advanced solid tumors (PROCLAIM-CX-072): a first-in-human, dose-finding study

BACKGROUND

Probody® therapeutics are antibody prodrugs designed to be activated by tumor-associated proteases. This conditional activation restricts antibody binding to the tumor microenvironment, thereby minimizing 'off-tumor' toxicity. Here, we report the phase 1 data from the first-in-human study of CX-072 (pacmilimab), a Probody immune checkpoint inhibitor directed against programmed death-ligand 1 (PD-L1), in combination with the anti-cytotoxic T-lymphocyte-associated protein 4 (anti-CTLA-4) antibody ipilimumab.

METHODS

Adults (n=27) with advanced solid tumors (naive to PD-L1/programmed cell death protein 1 or CTLA-4 inhibitors) were enrolled in the phase 1 combination therapy dose-escalation portion of this multicenter, open-label, phase 1/2 study (NCT03013491). Dose-escalation pacmilimab/ipilimumab followed a standard 3+3 design and continued until the maximum tolerated dose (MTD) was determined. Pacmilimab+ipilimumab was administered intravenously every 3 weeks for four cycles, followed by pacmilimab administered every 2 weeks as monotherapy. The primary objective was identification of dose-limiting toxicities and determination of the MTD. Other endpoints included the rate of objective response (Response Evaluation Criteria In Solid Tumors v.1.1).

RESULTS

Twenty-seven patients were enrolled in pacmilimab (mg/kg)+ipilimumab (mg/kg) dose-escalation cohorts: 0.3+3 (n=6); 1+3 (n=3); 3+3 (n=3); 10+3 (n=8); 10+6 (n=6); and 10+10 (n=1). Dose-limiting toxicities occurred in three patients, one at the 0.3+3 dose level (grade 3 dyspnea/pneumonitis) and two at the 10+6 dose level (grade 3 colitis, grade 3 increased aspartate aminotransferase). The MTD and recommended phase 2 dose was pacmilimab 10 mg/kg+ipilimumab 3 mg/kg administered every 3 weeks. Pacmilimab-related grade 3-4 adverse events (AEs) and grade 3-4 immune-related AEs were reported in nine (33%) and six (22%) patients, respectively. Three patients (11%) discontinued treatment because of AEs. The overall response rate was 19% (95% CI 6.3 to 38.1), with one complete (anal squamous cell carcinoma) and four partial responses (cancer of unknown primary, leiomyosarcoma, mesothelioma, testicular cancer). Responses lasted for >12 months in four patients.

CONCLUSIONS

The MTD and recommended phase 2 dose of pacmilimab (10 mg/kg)+ipilimumab (3 mg/kg) every 3 weeks is active and has a favorable tolerability profile.

CX-072 (pacmilimab), a Probody PD-L1 inhibitor, in advanced or recurrent solid tumors (PROCLAIM-CX-072): an open-label dose-finding and first-in-human study

BACKGROUND

Probody® therapeutics are antibody prodrugs that are activated in the tumor microenvironment by tumor-associated proteases, thereby restricting the activity to the tumor microenvironment and minimizing 'off-tumor' toxicity. We report dose-escalation and single-agent expansion phase data from the first-in-human study of CX-072 (pacmilimab), a Probody checkpoint inhibitor directed against programmed death-ligand 1 (PD-L1).

METHODS

In the dose-escalation phase of this multicenter, open-label study (NCT03013491), adults with advanced solid tumors (naive to programmed-death-1/PD-L1 or cytotoxic T-lymphocyte-associated antigen 4 inhibitors) were enrolled into one of seven dose-escalation cohorts, with pacmilimab administered intravenously every 14 days. The primary endpoints were safety and determination of the maximum tolerated dose (MTD). In the expansion phase, patients with one of six prespecified malignancies (triple-negative breast cancer [TNBC]; anal squamous cell carcinoma [aSCC]; cutaneous SCC [cSCC]; undifferentiated pleomorphic sarcoma [UPS]; small bowel adenocarcinoma [SBA]; and thymic epithelial tumor [TET]); or high tumor mutational burden (hTMB) tumors were enrolled. The primary endpoint was objective response (Response Evaluation Criteria In Solid Tumors v.1.1).

RESULTS

An MTD was not reached with doses up to 30 mg/kg. A recommended phase 2 dose (RP2D) of 10 mg/kg was chosen based on pharmacokinetic and pharmacodynamic findings in the expansion phase. Ninety-eight patients enrolled in the expansion phase: TNBC (n=14), aSCC (n=14), cSCC (n=14), UPS (n=20), SBA (n=14), TET (n=8), and hTMB tumors (n=14). Of 114 patients receiving pacmilimab at the RP2D, grade ≥3 treatment-related adverse events (TRAEs) were reported in 10 patients (9%), serious TRAEs in six patients (5%), and treatment discontinuation due to TRAEs in two patients (2%). Grade ≥3 immune-related AEs occurred in two patients (rash, myocarditis). High PD-L1 expression (ie, >50% Tumor Proportion Score) was observed in 22/144 (19%) patients. Confirmed objective responses were observed in patients with cSCC (n=5, including one complete response), hTMB (n=4, including one complete response), aSCC (n=2), TNBC (n=1), UPS (n=1), and anaplastic thyroid cancer (n=1).

CONCLUSIONS

Pacmilimab can be administered safely at the RP2D of 10 mg/kg every 14 days. At this dose, pacmilimab had a low rate of immune-mediated toxicity and showed signs of antitumor activity in patients not selected for high PD-L1 expression.

TRIAL REGISTRATION NUMBER

NCT03013491.

Model-Informed Drug Development of the Masked Anti-PD-L1 Antibody CX-072

CX-072 is an anti-PD-L1 (programmed death ligand 1) Probody therapeutic (Pb-Tx) designed to be preferentially activated by proteases in the tumor microenvironment and not in healthy tissue. Here, we report the model-informed drug development of CX-072. A quantitative systems pharmacology (QSP) model that captured known mechanisms of Pb-Tx activation, biodistribution, elimination, and target engagement was used to inform clinical translation. The QSP model predicted that a trough level of masked CX-072 (intact CX-072) of 13-99 nM would correspond to a targeted, 95% receptor occupancy in the tumor. The QSP model predictions appeared consistent with preliminary human single-dose pharmacokinetic (PK) data following CX-072 0.03-30.0 mg/kg as monotherapy: CX-072 circulated predominantly as intact CX-072 with minimal evidence of target-mediated drug disposition. A preliminary population PK (POPPK) analysis based upon 130 subjects receiving 0.03-30.0 mg/kg as monotherapy included a provision for a putative time-dependent and dose-dependent antidrug antibody (ADA) effect on clearance (CL) with a mixture model. Preliminary POPPK estimates for intact CX-072 time-invariant CL and volume of distribution were 0.306 L/day and 4.84 L, respectively. Exposure-response analyses did not identify statistically significant relationships with best change from baseline sum of measurements and either adverse events of grade ≥ 3 or of special interest. Simulations suggested that > 95% of patients receiving CX-072 10 mg/kg every two weeks would exceed the targeted trough level regardless of ADA, and that dose adjustment by body weight was not necessary, supporting a fixed 800 mg dose for evaluation in phase II.

Preliminary clinical pharmacokinetics and dose-response to support a phase II dose selection for CX-2009: A masked probody drug conjugate to CD166

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Background: PROBODY therapeutics are antibody prodrugs with cleavable peptide masks designed to reduce off-tumor, on-target toxicities. The mask blocks binding in the periphery and is removed by tumor-associated proteases resulting in intratumoral binding. CX-2009 is a PROBODY drug conjugate directed against CD166/ALCAM, which is a target overexpressed in carcinomas but not suitable for traditional ADC targeting because it is expressed in normal epithelium. CX-2009 is conjugated to DM4, a potent microtubule inhibitor. Here we report preliminary clinical pharmacokinetic (PK) and exploratory dose-response (DR) analyses for CX-2009 from the ongoing phase 1/2 PROCLAIM-CX-2009 study (NCT03149549). Methods: Human PK and anti-drug antibody (ADA) data were obtained at selected times post-dose following IV 0.25–10 mpk CX-2009 Q3W and of 6 mpk Q2W. Covariates were selected for population PK (POPPK) based on multivariate screening at P< 0.01. Preliminary exploratory DR analyses were conducted for selected endpoints including adverse events of special interest and response data (CR, PR, SD, and PD). Results: Preliminary CX-2009 PK data from 92 subjects were available as of October 2019. Median free DM4 levels circulated at ≤0.3% of Total CX-2009 (masked + activated CX-2009) levels across the 1–10 mpk dose levels. A two-compartment POPPK model with linear elimination was fit to the Intact (masked form) CX-2009 data. The preliminary CX-2009 POPPK model estimates for Intact CX-2009 clearance (CL), volume of distribution, and half-life were 0.47 L/day, 4.51 L, and 7.14 days, respectively, with 91% of CX-2009 circulating as Intact CX-2009. ADA was not a statistically significant covariate on Intact CX-2009 CL. Evidence of clinical activity was observed at doses of 4 mpk Q3W or higher. DR analysis suggested that the frequency of grade ≥3 ocular toxicity events increased significantly at dose equivalents ≥8 mpk Q3W. POPPK simulations suggested that the targeted 90 nM trough concentration (based on nonclinical data) would be contained within the 90% prediction interval of predicted Intact CX-2009 levels following CX-2009 7 mpk. Conclusions: Preliminary CX-2009 PK data following CX-2009 0.25-10 mpk suggest that CX-2009 circulates predominantly as Intact CX-2009, and that Intact CX-2009 PK is not strongly influenced by target-mediated drug disposition or ADA. Preliminary DR and POPPK simulations support further evaluation of 7 mpk CX-2009 Q3W in selected cohort expansions. Clinical trial information: NCT03149549 .

Preliminary population pharmacokinetics supports phase II dose selection for masked anti-PD-L1 antibody CX-072

3602

Background: PROBODY therapeutics (Pb-Tx) are antibody prodrugs designed to reduce off-tumor, on-target toxicities. The mask inhibits Pb-Tx binding in the periphery yet can be removed by tumor-associated proteases, restricting target engagement to the tumor. This is the first report of preliminary clinical pharmacokinetic (PK) analysis supporting selection of the phase II dose for CX-072, an anti–PD-L1 Pb-Tx, from the ongoing phase I/II PROCLAIM-CX-072 study (NCT03013491). Methods: A quantitative systems pharmacology (QSP) model1 was used to project the CX-072 plasma trough level (Cmin) corresponding to 95% intratumoral receptor occupancy (RO). Human PK and anti-drug antibody (ADA) data were obtained at selected times postdose following IV administration of 0.03–30 mpk CX-072 in PROCLAIM-CX-072. Population PK (POPPK) modeling was performed with NONMEM v7.3.0. Exploratory analysis and simulations were done with R v3.3.1 or later. Covariates were selected for POPPK using forward addition ( P<0.05) followed by backward deletion ( P<0.01). Results: The preliminary POPPK analyses were informed using available PK data as of August, 2019 from 135 subjects receiving CX-072 Q2W as monotherapy in the dose-escalation and expansion cohorts of PROCLAIM-CX-072. A mixture model was used to capture time- and dose-dependent apparent ADA effect on clearance (CL). The preliminary POPPK model estimates for CX-072 CL and volume of distribution (Vd) were 0.306 L/day and 4.84 L, respectively. Statistically significant covariate effects included body weight on the central Vd and CL, and albumin on CL. The QSP model predicted a CX-072 Cmin of 13–99 nM would be required for 95% intratumoral RO. POPPK simulations suggested that >95% of patients receiving CX-072 10 mg/kg Q2W would meet or exceed this targeted Cmin regardless of ADA. Additional observed data indicated that the majority of patients receiving 10 mpk CX-072 Q3W × 4 with 3 mpk ipilimumab (IPI) Q3W × 4 in the CX-072-IPI combination part of PROCLAIM-CX-072 maintained the targeted Cmin. Simulations did not suggest there would be a clinically meaningful change in exposure following a fixed dose of CX-072 800 mg relative to the 10 mpk weight-based dose. Conclusions: Preliminary PK analysis supports selection of 800 mg CX-072 Q2W as the recommended monotherapy dose and 800 mg Q3W when combined with IPI. The combination of 800 mg CX-072 + 3 mpk IPI Q3W × 4 doses, followed by monotherapy administration of 800 mg CX-072 Q2W is being further explored in phase II. Reference: 1) Stroh M et al. CPT. 2019(9):676-84. Clinical trial information: NCT03013491 .

Evidence of intratumoral localization, activation, and immunomodulatory effect of CX-072, a probody therapeutic targeting PD-L1, in a phase I/II trial

3108

Background: PROBODY therapeutics (Pb-Tx) are masked antibodies designed to be selectively activated in the tumor microenvironment by tumor-associated proteases and to remain largely inactive in normal tissue. CX-072, a Pb-Tx directed against PD-L1, is designed to reduce the potential for immune-associated adverse events in normal tissues while maintaining anti-tumor activity. CX-072 is being investigated in PROCLAIM-CX-072 (NCT03013491), a first-in-human phase 1/2 trial. CX-072 is administered as monotherapy or in combination with ipilimumab to patients with metastatic or recurrent solid tumors or lymphomas for which approved PD-1/-L1–based therapy is not available. We present the updated results of a tissue-based biomarker program designed to assess activation, localization, and mechanism of action of CX-072 in patient tumors. Methods: Tumor biopsies were collected during the screening phase, and also 3–5 days after the first or third dose of 0.3–30 mg/kg CX-072. Tumor-associated protease activity was measured by tissue zymography. Intratumoral CX-072 activation was measured using capillary immunoelectrophoresis, and PD-L1 levels were measured by an ultrasensitive ELISA. Intratumoral CD8 expression was analyzed using immunohistochemistry. Intact and total CX-072 in plasma were measured by LC-MS/MS. Results: Twenty-six of 30 (87%) evaluable predose biopsies had detectable levels of relevant protease activity. Intratumoral activation of CX-072 was quantifiable in 3 of 8 (38%) biopsies from patients treated with CX-072 at 3 mg/kg and in 12 of 12 (100%) biopsies from patients treated with ≥10 mg/kg. In contrast, CX-072 remained predominantly in the intact form in circulation. The molar ratio of activated intratumoral CX-072 to total intratumoral PD-L1 ranged from ~14x to > 100x in patients dosed at 10 mg/kg, and the calculated tumor receptor occupancy for these patients was ≥99%, congruent with quantitative systems pharmacology model predictions. An increase in CD8+ T cells and elevation of cytotoxic T-cell markers was observed in the tumors of 11 of 18 (61%) CX-072 monotherapy patients, consistent with inhibition of the PD-L1 pathway. Conclusions: These results demonstrate that the Pb-Tx CX-072 behaves as designed in patients. Clinical trial information: NCT03013491 .

CX-2009, a CD166-directed probody drug conjugate (PDC): Results from the first-in-human study in patients (Pts) with advanced cancer including breast cancer (BC)

526

Background: CX-2009 is a PROBODY drug conjugate (PDC) directed against CD166 (ALCAM) and conjugated to DM4, a potent microtubule inhibitor (MTI). CD166 is overexpressed in carcinomas but is also ubiquitously expressed in normal epithelium and thus has not been previously considered a viable target for a traditional antibody drug conjugate. PDCs have a peptide mask that blocks normal tissue binding and can be removed by tumor-associated proteases, thereby limiting off-tumor/on-target binding. CX-2009 demonstrated preclinical activity in multiple solid tumor models. Here we report results of the first in human study in patients with advanced cancer. Methods: In this phase I multi-part dose-escalation study, pts with advanced solid tumors received CX-2009 0.25–10 mpk IV every 14 or 21 days (Q2W or Q3W). Tumor types were selected based on expected high CD166 expression and MTI sensitivity. Results: The dose-escalation phase of the trial enrolled 43 pts; 49 additional pts were subsequently enrolled between 4–10 mpk to collect biomarker data and define the recommended phase II dose (RP2D), for a total of 92 pts as of 30 Nov 2019 (39 pts with breast cancer [BC], 22 ovarian [OC], 12 non-small cell lung [NSCLC], 9 head/neck squamous cell [HNSCC], 10 other) with a median of 6 (range 1–19) prior therapies. Median number of CX-2009 doses was 2 (range, 1–15). For Q3W dosing, one dose limiting toxicity (DLT; grade 3 vomiting) was observed at 8 mpk; MTD was not reached up to 10 mpk. The RP2D for Q3W schedule was 7 mpk based on safety, dose-response, and population pharmacokinetic simulations. Q2W dosing continues; DLTs were observed at 6 mpk. Common treatment-related adverse events (TRAEs) at 7 mpk (n=9) were nausea (44%), fatigue, infusion-related reactions (both 33%), vomiting and arthralgias (both 22%). Grade 3 TRAEs occurred in 2 pts (nausea/vomiting; peripheral neuropathy). No pts discontinued at 7 mpk due to TRAEs. Ocular toxicity was dose dependent; mild to moderate reversible keratitis/blurred vision was seen in 3 pts at 7 mpk and mitigated by ocular prophylaxis. Partial responses were seen in 8 pts (2 confirmed, both HR+/HER2- BC) treated between 4–10 mpk, including BC (n=5), OC (n=2), and HNSCC (n=1). SD (≥1 on-study scan) was observed in 21 pts, 5 had SD ≥3 mos. Conclusions: CX-2009 at 7 mpk is the RP2D on Q3W schedule. Phase II expansion has begun in pts with HR+/HER2- BC. The Q2W schedule will continue to enroll pts to define the RP2D. CX-2009 will also be studied in combination with CX-072, a PD-L1 PROBODY therapeutic ( NCT03149549 ) Clinical trial information: NCT03149549 .

Abstract 212: CD166-DM4 probody drug conjugate (CX-2009) treatment of 198 patient-derived xenograft models (PDX) in a mouse clinical trial format

Ideal targets for antibody drug conjugates (ADC) are highly and homogeneously expressed on tumor cells in a wide variety of tumor types and in a high proportion of patients. Such targets should also be efficient cellular internalizers and have limited expression on normal tissues. Unfortunately, targets that meet all these criteria are rare. Probody™ drug conjugates (PDCs) are masked antibody prodrugs designed for activation by tumor-associated proteases. PDCs are designed to direct drug activity to the tumor microenvironment by exploiting the dysregulation of tumor protease activity that is the hallmark of most cancers. The Probody platform is designed to minimize interaction with healthy tissues, mitigate “on-target” toxicity regardless of expression outside of the tumor, and greatly expand the number of potential ADC targets. CD166 (ALCAM) is one such novel target. It is expressed at high levels in a high proportion of patients across multiple cancer types, but it is also on healthy tissues, including lung, gastro-intestinal tract, and liver. CX-2009, an investigational SPDB-DM4 PDC targeting CD166, is currently being evaluated in PROCLAIM CX-2009, a clinical phase I/II trial (NCT03149549). CX-2009 exhibited robust preclinical activity against cell-line derived xenograft (CDX) models across various solid tumor indications. Because the DM4 mechanism of action is similar to that of taxane-based chemotherapy, CX-2009 is being evaluated in the clinic for cancer types that respond to microtubule inhibitors and have prevalent CD166 expression. To help further inform patient selection for clinical studies, CX-2009 is being evaluated in 198 PDX models using a murine clinical trial format in collaboration with South Texas Accelerated Research Therapeutics (START). Each mouse is engrafted with a patient’s resected tumor sample that has not been passaged in vitro, and when kept minimally passaged in vivo, may more faithfully recapitulate the tumor biology and response to therapeutics than CDX models. The PDX models are dosed with 5mg/kg of CX-2009 every 2 weeks for 6 weeks via i.v. (q2wX3), and tumor volume is measured twice per week. Currently, we have dosed 66 breast, lung, and ovarian PDX models, obtaining an end-of-study response rate of 21% using clinically defined criteria, e.g. complete response (CR) plus partial response (PR), and a 29% disease-control rate (DCR). Relative to untreated controls, 43% of CX-2009-treated tumors yielded tumor growth inhibition (TGI) of greater than fifty percent. Because of the large cohort data set, this effort can potentially inform patient selection for clinical studies based on correlating efficacy with CD166 expression, tumor subtype, tumor growth rate (doubling time), and taxane sensitivity. PROBODY is a trademark of CytomX Therapeutics, Inc.

Citation Format: Bob Y. Liu, Joel Shen, Matthias Will, Sreeni Yalamanchili, Judi Gordon, Mark Stroh, Jennifer Richardson, Annie Weaver, Luc Desnoyer, Marcia Belvin, Michael Kavanaugh, Siew Schleyer. CD166-DM4 probody drug conjugate (CX-2009) treatment of 198 patient-derived xenograft models (PDX) in a mouse clinical trial format [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 212.

Quantitative Systems Pharmacology Model of a Masked, Tumor-Activated Antibody

PROBODY therapeutics (Pb‐Tx) are protease‐activatable prodrugs of monoclonal antibodies (mAbs) designed to target tumors where protease activity is elevated while avoiding normal tissue. They are composed of a parental mAb, a mask that inhibits antibody binding to target, and a protease‐cleavable substrate between the mask and the mAb. We report a quantitative systems pharmacology model for the rational design and clinical translation of Pb‐Tx. The model adequately described monkey pharmacokinetic data following the administration of six anti‐CD166 Pb‐Tx of varying mask strength and substrate cleavability and captured the trend of decreasing Pb‐Tx systemic clearance with increasing mask strength. Projections to humans suggested both higher levels of Pb‐Tx in tumor relative to parental mAb and an optimal mask strength for maximizing tumor receptor–mediated uptake. Simulations further suggested the majority of circulating species in humans would be intact/masked Pb‐Tx, with no significant flux of cleaved/activated species from tumor to the systemic compartment.

A PK/PD Analysis of Circulating Biomarkers and Their Relationship to Tumor Response in Atezolizumab-Treated non-small Cell Lung Cancer Patients

To assess circulating biomarkers as predictors of antitumor response to atezolizumab (anti-programmed death-ligand 1 (PD-L1), Tecentriq) serum pharmacokinetic (PK) and 95 plasma biomarkers were analyzed in 88 patients with relapsed/refractory non-small cell lung cancer (NSCLC) receiving atezolizumab i.v. q3w (10-20 mg/kg) in the PCD4989g phase I clinical trial. Following exploratory analyses, two plasma biomarkers were chosen for further study and correlation with change in tumor size (the sum of the longest diameter) was assessed in a pharmacokinetic/pharmacodynamic (PK/PD) tumor modeling framework. When longitudinal kinetics of biomarkers and tumor size were modeled, tumor shrinkage was found to significantly correlate with area under the curve (AUC), baseline factors (metastatic sites, liver metastases, and smoking status), and relative change in interleukin (IL)-18 level from baseline at day 21 (RCFB_{IL -18,d21} ). Although AUC was a major predictor of tumor shrinkage, the effect was estimated to dissipate with an average half-life of 80 days, whereas RCFB_{IL -18,d21} seemed relevant to the duration of the response.

Clinical Pharmacokinetics and Pharmacodynamics of Atezolizumab in Metastatic Urothelial Carcinoma

Atezolizumab, a humanized immunoglobulin G1 (IgG1) monoclonal antibody targeting human programmed death-ligand 1 (PD-L1), is US Food and Drug Administration (FDA) approved in metastatic urothelial carcinoma (MUC) and is being investigated in various malignancies. This analysis based upon 906 patients from two phase I and one phase II MUC studies, is the first report of the clinical pharmacokinetics (PK) and pharmacodynamics (PD) of atezolizumab. Atezolizumab exhibited linear PK over a dose range of 1-20 mg/kg, including the labeled 1,200 mg dose. The clearance, volume of distribution, and terminal half-life estimates from population pharmacokinetic (PopPK) analysis of 0.200 L/day, 6.91 L, and 27 days, respectively, were as expected for an IgG1. Exposure-response analyses did not identify statistically significant relationships with either objective response rate or adverse events of grades 3-5 or of special interest. None of the statistically significant covariates from PopPK (body weight, gender, antitherapeutic antibody, albumin, and tumor burden) would require dose adjustment.

Randomized Phase II Trial of Parsatuzumab (Anti-EGFL7) or Placebo in Combination with FOLFOX and Bevacizumab for First-Line Metastatic Colorectal Cancer

Lessons Learned.

These negative phase II results for parsatuzumab highlight the challenges of developing an agent intended to enhance the efficacy of vascular endothelial growth factor inhibition without the benefit of validated pharmacodynamic biomarkers or strong predictive biomarker hypotheses.

Any further clinical development of anti‐EGFL7 is likely to require new mechanistic insights and biomarker development for antiangiogenic agents.

Background.

EGFL7 (epidermal growth factor‐like domain 7) is a tumor‐enriched vascular extracellular matrix protein that supports endothelial cell survival. This phase II trial evaluated the efficacy of parsatuzumab (also known as MEGF0444A), a humanized anti‐EGFL7 IgG₁ monoclonal antibody, in combination with modified FOLFOX6 (mFOLFOX6) (folinic acid, 5‐fluorouracil, and oxaliplatin) bevacizumab in patients with previously untreated metastatic colorectal cancer (mCRC).

Methods.

One‐hundred twenty‐seven patients were randomly assigned to parsatuzumab, 400 mg, or placebo, in combination with mFOLFOX6 plus bevacizumab, 5 mg/kg. Treatment cycles were repeated every 2 weeks until disease progression or unacceptable toxicity for a maximum of 24 months, with the exception of oxaliplatin, which was administered for up to 8 cycles.

Results.

The progression‐free survival (PFS) hazard ratio was 1.17 (95% confidence interval [CI], 0.71–1.93; p = .548). The median PFS was 12 months for the experimental arm versus 11.9 months for the control arm. The hazard ratio for overall survival was 0.97 (95% CI, 0.46–2.1; p = .943). The overall response rate was 59% in the parsatuzumab arm and 64% in the placebo arm. The adverse event profile was similar in both arms.

Conclusions.

There was no evidence of efficacy for the addition of parsatuzumab to the combination of bevacizumab and chemotherapy for first‐line mCRC.

A survey of new oncology drug approvals in the USA from 2010 to 2015: a focus on optimal dose and related postmarketing activities

The maximally tolerated dose (MTD) of cytotoxic agents has historical precedence in treating cancer, as it was believed that dose and therapeutic effect are intrinsically linked and that the MTD would provide greatest therapeutic value. With molecularly targeted agents, the premise of preventing toxicity to normal tissues while modulating tumor growth provides a potential for an increased therapeutic window. Results from these targeted agents suggest we are entering an era of chronic cancer management, which will require design of regimens with long-term tolerability. A corresponding switch from MTD-based (toxicity-driven) dosing strategies to alternative paradigms is also expected. The challenge with these targeted agents is to fully understand the complex relationship between pharmacokinetics, pharmacodynamics, and safety and efficacy in early-stage trials, so that the optimal dose and schedule for registration trials may be identified. This review provides a systematic survey of the applications submitted to the United States Food and Drug Administration (FDA) for oncology indications, from 2010 through early 2015, and summarizes the dose selection rationale for registrational trials, the relationship of the MTD to outcomes of the final label dose, the postmarketing requirements or commitments related to dose optimization activities, the role of biomarkers, and typical exposure-response modeling methods.

Challenges and Opportunities for Quantitative Clinical Pharmacology in Cancer Immunotherapy: Something Old, Something New, Something Borrowed, and Something Blue

Cancer immunotherapy (CIT) initiates or enhances the host immune response against cancer. Following decades of development, patients with previously few therapeutic options may now benefit from CIT. Although the quantitative clinical pharmacology (qCP) of previous classes of anticancer drugs has matured during this time, application to CIT may not be straightforward since CIT acts via the immune system. Here we discuss where qCP approaches might best borrow or start anew for CIT.

Onartuzumab with or without bevacizumab in combination with weekly paclitaxel does not prolong QTc or adversely affect other ECG parameters in patients with locally recurrent or metastatic triple-negative breast cancer

PURPOSE

The potential effect of onartuzumab, when administered with or without bevacizumab in combination with weekly paclitaxel, on the corrected QT interval (QTc) and other electrocardiogram (ECG) parameters, was investigated in a randomized, phase 2 study OAM4861g of first- or second-line therapy in patients with locally recurrent or metastatic triple-negative breast cancer.

METHODS

Triplicate 12-lead ECGs were recorded at screening, pre- and post-dose on day 1 of cycles 1, 2, and 4, and at the study drug discontinuation visit (SDDV). Onartuzumab serum samples were collected pre- and post-dose on day 1 of cycles 1-4 and at the SDDV. Fridericia's correction was applied to QT recordings (QTcF), and change from baseline (ΔQTcF) was calculated. Post-baseline measurements were reported as baseline-adjusted control arm (placebo plus bevacizumab plus paclitaxel)-corrected values (ΔΔQTcF). Categorical ECG findings were noted. Linear mixed effects modeling evaluated a potential concentration-ΔQTcF relationship.

RESULTS

Out of 185 enrolled patients, 165 patients had ECG-evaluable data for analyses. Similar ΔQTcF and ΔΔQTcF values were observed across all treatment arms, with mean increase <10 and <7 ms, respectively, across all time points. Similar changes in heart rate, PR interval, and QRS duration were noted across all treatment arms. Incidences of abnormal ECG findings of clinical interest were comparable in the onartuzumab-containing arms and the control arm. No concentration-ΔQTcF relationship was evident at onartuzumab serum concentrations up to 1,200 μg/ml.

CONCLUSIONS

These data suggest that onartuzumab, at the dose and exposures studied in this clinical trial, does not meaningfully affect the QTcF interval.

Translation of anticancer efficacy from nonclinical models to the clinic

Mouse cancer models have provided critical insights into tumor biology; however, clinical translation of these findings has been challenging. This perspective posits that factors impacting on successful translation start with limitations in capturing human cancer pathophysiology and end with challenges in generating robust translatable preclinical end points. A comprehensive approach that considers clinically relevant mouse models with both an integrated biomarker strategy and a complementary modeling and simulation effort will strengthen the current oncology drug development paradigm.

Lack of meaningful effect of ridaforolimus on the pharmacokinetics of midazolam in cancer patients: model prediction and clinical confirmation

Ridaforolimus, a unique non-prodrug analog of rapamycin, is a potent inhibitor of mTOR under development for cancer treatment. In vitro data suggest ridaforolimus is a reversible and time-dependent inhibitor of CYP3A. A model-based evaluation suggested an increase in midazolam area under the curve (AUC(0- ∞)) of between 1.13- and 1.25-fold in the presence of therapeutic concentrations of ridaforolimus. The pharmacokinetic interaction between multiple oral doses of ridaforolimus and a single oral dose of midazolam was evaluated in an open-label, fixed-sequence study, in which cancer patients received a single oral dose of 2 mg midazolam followed by 5 consecutive daily single oral doses of 40 mg ridaforolimus with a single dose of 2 mg midazolam with the fifth ridaforolimus dose. Changes in midazolam exposure were minimal [geometric mean ratios and 90% confidence intervals: 1.23 (1.07, 1.40) for AUC(0-∞) and 0.92 (0.82, 1.03) for maximum concentrations (C(max)), respectively]. Consistent with model predictions, ridaforolimus had no clinically important effect on midazolam pharmacokinetics and is not anticipated to be a perpetrator of drug-drug interactions (DDIs) when coadministered with CYP3A substrates. Model-based approaches can provide reasonable estimates of DDI liability, potentially obviating the need to conduct dedicated DDI studies especially in challenging populations like cancer patients.

Simultaneous pharmacokinetic model for rolofylline and both M1-trans and M1-cis metabolites

Rolofylline is a potent, selective adenosine A1 receptor antagonist that was under development for the treatment of patients with acute congestive heart failure and renal impairment. Rolofylline is metabolized primarily to the pharmacologically active M1-trans and M1-cis metabolites (metabolites) by cytochrome P450 (CYP) 3A4. The aim of this investigation was to provide a pharmacokinetic (PK) model for rolofylline and metabolites following intravenous administration to healthy volunteers. Data included for this investigation came from a randomized, double-blind, dose-escalation trial in four groups of healthy volunteers (N=36) where single doses of rolofylline, spanning 1 to 60 mg ,were infused over 1-2 h. The rolofylline and metabolite data were analyzed simultaneously using NONMEM. The simultaneous PK model comprised, in part, a two-compartment linear PK model for rolofylline, with estimates of clearance and volume of distribution at steady-state of 24.4 L/h and 239 L, respectively. In addition, the final PK model contained provisions for both conversion of rolofylline to metabolites and stereochemical conversion of M1-trans to M1-cis. Accordingly, the final model captured known aspects of rolofylline metabolism and was capable of simultaneously describing the PK of rolofylline and metabolites in healthy volunteers.

A single supratherapeutic dose of ridaforolimus does not prolong the QTc interval in patients with advanced cancer

Purpose

This dedicated QTc study was designed to evaluate the effect of the mammalian target of rapamycin inhibitor, ridaforolimus, on the QTc interval in patients with advanced malignancies.

Methods

We conducted a fixed-sequence, single-blind, placebo-controlled study. Patients (n = 23) received placebo on day 1 and a single 100-mg oral dose of ridaforolimus on day 2 in the fasted state. Holter electrocardiogram (ECG) monitoring was performed for 24 h after each treatment, and blood ridaforolimus concentrations were measured for 24 h after dosing. The ECGs were interpreted in a blinded fashion, and the QT interval was corrected using Fridericia’s formula (QTcF). After a washout of at least 5 days, 22 patients went on to receive a therapeutic regimen of ridaforolimus (40 mg orally once daily for 5 days per week).

Results

The upper limit of the two-sided 90 % confidence interval for the placebo-adjusted mean change from baseline in QTcF was <10 ms at each time point. No patient had a QTcF change from baseline >30 ms or QTcF interval >480 ms. Geometric mean exposure to ridaforolimus after the single 100-mg dose was comparable to previous experience with the therapeutic regimen. There appeared to be no clear relationship between individual QTcF change from baseline and ridaforolimus blood concentrations. Ridaforolimus was generally well tolerated, with adverse events consistent with prior studies.

Conclusions

Administration of the single 100-mg dose of ridaforolimus did not cause a clinically meaningful prolongation of QTcF, suggesting that patients treated with ridaforolimus have a low likelihood of delayed ventricular repolarization.

Electronic supplementary material

The online version of this article (doi:10.1007/s00280-012-1942-7) contains supplementary material, which is available to authorized users.

First-in-human study of AMG 900, an oral pan-Aurora kinase inhibitor, in adult patients (pts) with advanced solid tumors

3009

Background: Aurora kinases A, B, and, C play essential roles in regulating cell division. Overexpression of aurora A and B in human tumors is associated with high proliferation rates and poor prognosis. AMG 900 is an investigational, orally administered, highly selective inhibitor of aurora A, B, and C that demonstrated activity in drug-resistant cell lines and human tumor xenografts. This study evaluated the safety, tolerability, pharmacokinetics (PK), and pharmacodynamics of AMG 900. Methods: Key eligibility criteria: ≥ 18 years old, advanced solid tumors, measurable disease, ECOG ≤ 2, and adequate organ function. AMG 900 was administered orally daily for 4 consecutive days (D) every 2 weeks (Q2W). In the dose-escalation phase, the starting dose was 1 mg and was escalated by 100% in subsequent cohorts (1 pt/cohort) until dose limiting toxicity (DLT) or grade 2 (G2) AMG 900-related toxicity occurred in the first 28 D. Dose escalation continued in a standard 3+3 design at ≤ 25% if DLT occurred or ≤ 50% if G2 related toxicity occurred. The maximum tolerated dose (MTD) was determined without prophylactic G-CSF support. Results: As of OCT 2011, 19 pts (1 pt at 1, 2, 4, and 8 mg; 3 pts at 16 mg; and 6 pts at 24 and 30 mg) had received ≥ 1 dose of AMG 900. Demographics were 58% women, median age 60 (32-77) years, and ECOG 0/1, 63%/37%. There were 4 DLTs: G4 neutropenia > 7 days at 24 mg (n=1) and 30 mg (n=1); G4 neutropenia > 7 days + G4 thrombocytopenia at 30 mg (n=1); and febrile neutropenia (FN) at 30 mg (n=1). MTD without G-CSF support was 24 mg. 89% of pts had treatment-related adverse events (AEs). G≥3 treatment-related AEs were neutropenia, 8 (42%); leukopenia, 4 (21%); anemia, 2 (11%); thrombocytopenia, 1 (5%); and FN, 1 (5%). Preliminary PK showed no obvious departures from dose-proportionality with a half-life of ~16 h. Tumor-response data were available for 17 pts: stable disease, 13 pts (range 0.4 to 43.7 wks); progressive disease, 4 pts. One pt (16 mg cohort) with recurrent ovarian cancer had 16% tumor shrinkage and 45% decrease in CA-125 (SD > 6 months). Conclusions: AMG 900 administered at 24 mg daily for 4D Q2W is the recommended dose for phase 2 trials. Dose escalation is now ongoing to determine the MTD with prophylactic G-CSF.

RNA-induced silencing complex-bound small interfering RNA is a determinant of RNA interference-mediated gene silencing in mice

Deeper knowledge of pharmacokinetic and pharmacodynamic (PK/PD) concepts for RNA therapeutics is important to streamline the drug development process and for rigorous selection of best performing drug candidates. Here we characterized the PK/PD relationship for small interfering RNAs (siRNAs) targeting luciferase by examining siRNA concentration in plasma and liver, the temporal RNA-induced silencing complex binding profiles, mRNA reduction, and protein inhibition measured by noninvasive bioluminescent imaging. A dose-dependent and time-related decrease in bioluminescence was detected over 25 days after a single treatment of a lipid nanoparticle-formulated siRNA targeting luciferase messenger RNA. A direct relationship was observed between the degree of in vivo mRNA and protein reduction and the Argonaute2 (Ago2)-bound siRNA fraction but not with the total amount of siRNA found in the liver, suggesting that the Ago2-siRNA complex is the key determinant of target inhibition. These observations were confirmed for an additional siRNA that targets endogenously expressed Sjögren syndrome antigen B (Ssb) mRNA, indicating that our observations are not limited to a transgenic mouse system. Our data provide detailed information of the temporal regulation of siRNA liver delivery, Ago2 loading, mRNA reduction, and protein inhibition that are essential for the rapid and cost-effective clinical development of siRNAs therapeutics.

Gamma-ray emission concurrent with the nova in the symbiotic binary V407 Cygni

Novae are thermonuclear explosions on a white dwarf surface fueled by mass accreted from a companion star. Current physical models posit that shocked expanding gas from the nova shell can produce x-ray emission, but emission at higher energies has not been widely expected. Here, we report the Fermi Large Area Telescope detection of variable gamma-ray emission (0.1 to 10 billion electron volts) from the recently detected optical nova of the symbiotic star V407 Cygni. We propose that the material of the nova shell interacts with the dense ambient medium of the red giant primary and that particles can be accelerated effectively to produce pi(0) decay gamma-rays from proton-proton interactions. Emission involving inverse Compton scattering of the red giant radiation is also considered and is not ruled out.

Model-based decision making in early clinical development: minimizing the impact of a blood pressure adverse event

We describe how modeling and simulation guided program decisions following a randomized placebo-controlled single-rising oral dose first-in-man trial of compound A where an undesired transient blood pressure (BP) elevation occurred in fasted healthy young adult males. We proposed a lumped-parameter pharmacokinetic-pharmacodynamic (PK/PD) model that captured important aspects of the BP homeostasis mechanism. Four conceptual units characterized the feedback PD model: a sinusoidal BP set point, an effect compartment, a linear effect model, and a system response. To explore approaches for minimizing the BP increase, we coupled the PD model to a modified PK model to guide oral controlled-release (CR) development. The proposed PK/PD model captured the central tendency of the observed data. The simulated BP response obtained with theoretical release rate profiles suggested some amelioration of the peak BP response with CR. This triggered subsequent CR formulation development; we used actual dissolution data from these candidate CR formulations in the PK/PD model to confirm a potential benefit in the peak BP response. Though this paradigm has yet to be tested in the clinic, our model-based approach provided a common rational framework to more fully utilize the limited available information for advancing the program.

X-ray flares in early GRB afterglows

The Swift X-ray Telescope (XRT) has discovered that flares are quite common in early X-ray afterglows of gamma-ray bursts (GRBs), being observed in roughly 50% of afterglows with prompt follow-up observations. The flares range in fluence from a few per cent to approximately 100% of the fluence of the prompt emission (the GRB). Repetitive flares are seen, with more than four successive flares detected by the XRT in some afterglows. The rise and fall times of the flares are typically considerably smaller than the time since the burst. These characteristics suggest that the flares are related to the prompt emission mechanism, but at lower photon energies. We conclude that the most likely cause of these flares is late-time activity of the GRB central engine.

Quantum dots spectrally distinguish multiple species within the tumor milieu in vivo

A solid tumor is an organ composed of cancer and host cells embedded in an extracellular matrix and nourished by blood vessels. A prerequisite to understanding tumor pathophysiology is the ability to distinguish and monitor each component in dynamic studies. Standard fluorophores hamper simultaneous intravital imaging of these components. Here, we used multiphoton microscopy techniques and transgenic mice that expressed green fluorescent protein, and combined them with the use of quantum dot preparations. We show that these fluorescent semiconductor nanocrystals can be customized to concurrently image and differentiate tumor vessels from both the perivascular cells and the matrix. Moreover, we used them to measure the ability of particles of different sizes to access the tumor. Finally, we successfully monitored the recruitment of quantum dot-labeled bone marrow-derived precursor cells to the tumor vasculature. These examples show the versatility of quantum dots for studying tumor pathophysiology and creating avenues for treatment.

Multiphoton microscopy guides neurotrophin modification with poly(ethylene glycol) to enhance interstitial diffusion

Brain-derived neurotrophic factor (BDNF) is a promising therapeutic agent for the treatment of neurodegenerative diseases. However, the limited distribution of this molecule after administration into the brain tissue considerably hampers its efficacy. Here, we show how multiphoton microscopy of fluorescently tagged BDNF in brain-tissue slices provides a useful and rapid screening method for examining the diffusion of large molecules in tissues, and for studying the effects of chemical modifications-for example, conjugating with polyethylene glycol (PEG)-on the diffusion constant. This single variable, obtained by monitoring short-term diffusion in real time, can be effectively used for rational drug design. In this study on fluorescently tagged BDNF and BDNF-PEG, we identify slow diffusion as a major contributing factor to the limited penetration of BDNF, and demonstrate how chemical modification can be used to overcome this barrier.

Diffusion of nerve growth factor in rat striatum as determined by multiphoton microscopy

Neurotrophins such as nerve growth factor (NGF) may be useful for treating diseases in the central nervous system; our ability to harness the potential therapeutic benefit of NGF is directly related to our understanding of the fate of exogenously supplied factors in brain tissue. We utilized multiphoton microscopy to quantify the dynamic behavior of NGF in coronal, 400- micro m thick, fresh rat brain tissue slices. We administered a solution containing bioactive rhodamine nerve growth factor conjugate via pressure injection and monitored the dispersion in the striatal region of the coronal slices. Multiphoton microscopy facilitated repeated imaging deep ( approximately 200 micro m) into tissue slices with minimal photodamage of tissue and photobleaching of label. The pressure injection paradigm approximated diffusion from a point source, and we therefore used the corresponding solution to the diffusion equation to estimate an apparent diffusion coefficient in brain tissue (D(b)(34 degrees C)) of 2.75 +/- 0.24 x 10(-7) cm(2)/s (average +/- SE). In contrast, we determined a corresponding free diffusion coefficient in buffered solution (D(f)(34 degrees C)) of 12.6 +/- 0.9 x 10(-7) cm(2)/s using multiphoton fluorescence photobleaching recovery. The tortuosity, defined as the square root of the ratio of D(f) to D(b), was 2.14 and moderate in magnitude.

Cholera toxin binding affinity and specificity for gangliosides determined by surface plasmon resonance

The present study determines the affinity of cholera toxin for the ganglioside series GM1, GM2, GM3, GD1A, GD1B, GT1B, asialo GM1, globotriosyl ceramide, and lactosyl ceramide using real time biospecific interaction analysis (surface plasmon resonance, SPR). SPR shows that cholera toxin preferably binds to gangliosides in the following sequence: GM1 > GM2 > GD1A > GM3 > GT1B > GD1B > asialo-GM1. The measured binding affinity of cholera toxin for the ganglioside sequence ranges from 4.61 x 10-12 M for GM1 to 1.88 x 10-10 M for asialo GM1. The picomolar values obtained by surface plasmon resonance are similar to Kd values determined with whole-cell binding assays. Both whole-cell assays and SPR measurements on synthetic membranes are higher than free solution measurements by several orders of magnitude. This difference may be caused by the effects of avidity and charged lipid head-groups, which may play a major role in the binding between cholera toxin, the receptor, and the membrane surface. The primary difference between free solution binding studies and surface plasmon resonance studies is that the latter technique is performed on surfaces resembling the cell membrane. Surface plasmon resonance has the further advantage of measuring apparent kinetic association and dissociation rates in real time, providing direct information about binding events at the membrane surface.

A 'litmus test' for molecular recognition using artificial membranes

BACKGROUND

Sensitive and selective molecular recognition is important throughout biology. Certain organisms and toxins use specific binding at the cell surface as a first step towards invasion. A new series of biomolecular materials, with novel optical and interfacial properties, have been designed to sense molecular recognition events. These polymers, the diacetylenic lipids, have previously been shown to undergo chromatic transitions in response to virus binding to the surface of the material.

RESULTS

Gangliosides that specifically bind cholera toxin, heat-labile Escherichia coli enterotoxin and botulinum neurotoxin were incorporated into a matrix of diacetylenic lipids, 5-10% of which were derivatized with sialic acid. The lipids were self-assembled into Langmuir-Blodgett layers and polymerized with ultraviolet irradiation, yielding a polydiacetylene membrane with a characteristic blue color into which the ganglioside is non-covalently incorporated. When toxin is added, the polymerized membrane turns red. The response is specific and selective, and can be quantified by visible absorption spectrophotometry.

CONCLUSIONS

Polydiacetylenic lipid membranes offer a general 'litmus test' for molecular recognition at the surface of a membrane. A concentration of 20 ppm of protein could be detected using polymerized thin films. The speed, sensitivity and simplicity of the design offers a new and general approach towards the direct colorimetric detection of a variety of different molecules.

[Early operation for acute gallbladder as a therapeutic principle]

Between 1 January 1969 and 30 June 1984 904 patients with acute cholecystitis were treated as inpatients. Including 1976, initial treatment was conservative, and interval operation was recommended after 6-8 weeks. Commencing in 1977 early operation was preferred. Immediate operation within a few hours after admission and preparation for operation was done only in threatening or demonstrable complications of acute cholecystitis. Multimorbidity was highest (39%) in conservatively treated patients (n = 204), it was 26% in immediately operated patients (n = 201) and 23% in patients operated in the interval (n = 199). Early operation (n = 300) was associated with a multimorbidity of only 13%. Postoperative complications occurred most frequently (33%) after immediate operation, and in only 11% after early operation. Exploration of the choledochus was required in 27% of immediately operated cases and in only 19% of early and interval operations. Mortality after exclusively conservative treatment was 3%, after immediate operation 16%, after interval operation 3% and after early operation only 1.3%. Follow-up assessment of 137 primarily non-operated patients (7-15 years) showed a mortality of 48% on subsequently necessary immediate operation (16 out of 33 patients). No symptoms were seen in 14 out of 32 patients, only two of them had no gallstones. The high reliability of establishing the diagnosis (98% correct diagnosis) justifies early operation as preferred concept of treatment. Primary conservative treatment of acute cholecystitis and subsequently planned interval operation should be limited to justifiable exceptions.