Abstract LB096: Development of a next generation ROR1 targeting Protein Drug Conjugate (PDC)

The receptor tyrosine kinase ROR1 is a cell-surface onco-fetal protein expressed on a variety of solid tumours and haematological malignancies, which has limited expression on normal adult tissue. A functional role for ROR1 in tumorigenesis and disease progression has been demonstrated in a number of cancer indications. ROR1 is also involved in mediating drug resistance (for example to chemotherapies as well as to the targeted therapy T-DM1), activation of YAP/TAZ signalling and up-regulation of BMI-1. Consistent with this pleiotropic role, increased ROR1 expression correlates with poor clinical outcome in a number of cancer indications including triple negative breast cancer, ovarian cancer and lung adenocarcinoma. As a result, ROR1 has emerged as a highly attractive target for cancer therapy, and its limited expression on normal tissues make it particularly well suited for antibody and protein-drug conjugate (ADC and PDC) approaches. This has been fuelled by recent Phase I clinical data for the ROR1 ADC, VLS-101, in patients with advanced MCL and DLBCL and the potential of ROR1-targeting drug conjugates for the treatment of ROR1+ solid tumour indications. We report the development of novel, differentiated protein drug conjugates targeting ROR1 based on Variable New Antigen Receptor domains (VNARs). VNARs are the smallest antigen binding domain in the vertebrate kingdom and their small size and modular nature offer a number of potential benefits over full-length antibodies as the payload delivery vehicle in PDC approaches. We have applied our VNAR drug discovery platform, which includes novel linker-toxin combinations, to the development of potent and selective ROR1 targeting PDCs that are highly efficacious in ROR1+ patient derived xenograft (PDX) models of cancer. Homogenous drug conjugates were generated by Fc-fusion reformatting of ROR1 binding VNARs, and novel cleavable linker-toxin conjugates attached in a site-specific fashion. By exploiting proprietary crystal-structure information, a structure-guided approach was used to deliver VNAR-hFc drug conjugates with optimised drug-like properties. Though iterations of this approach, lead PDCs have been developed which cause potent ROR1-dependant killing of selected cancer cell-lines and elicit complete and durable regressions in PDX models of TNBC at doses that are very well tolerated. As the lead Candidate progresses toward clinical development, we anticipate that this excellent pre-clinical profile will translate to a highly differentiated product for the treatment of both solid tumor and haematological cancer indications. In addition, the flexible formatting accessible using our drug discovery platform has allowed us to readily access ROR1-targeting bi-paratopic and bi-specific therapeutic formats.

Citation Format: Graham Cotton, Jennifer Thom, Paul Trumper, Stacey Bell, Mark Wappett, Caroline Barelle, Marina Kovaleva, Andrew Porter, Estelle McLean, Chiara Saladino, Aidan McCann, Aaron Cranston, Tim Harrison. Development of a next generation ROR1 targeting Protein Drug Conjugate (PDC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr LB096.

Abstract 538: Exploiting the properties of VNAR domains for the development of novel efficacious protein drug conjugates targeting the oncofetal protein ROR1

The onco-embryonic receptor tyrosine kinase ROR1is a cell-surface protein expressed on a broad range of solid tumours and haematological malignancies but is largely absent from normal adult tissue. Increased ROR1 expression correlates with poor clinical outcome in a number of cancer indications, consistent with its functional role in tumorigenesis and disease progression. In addition, elevated expression has been associated with increased metastatic potential and drug resistance in breast cancer and non-small cell lung cancer. The oncofetal expression pattern of ROR1 coupled with its role in cancer pathology and therapy resistance makes it a highly attractive target for a protein-drug conjugate approach. Shark-derived Variable New Antigen Receptor domains (VNARs) are the smallest antigen binding domain in the vertebrate kingdom. We have developed a platform to enable VNAR-based drug discovery and used it to identify a series of highly potent protein-drug conjugates that target ROR1. Through screening VNAR phage libraries, high affinity ROR1 specific binders were isolated that bind distinct regions of the extracellular domain and showed species cross reactivity (mouse, rat and human). By exploiting the modular nature of the VNAR domains, multiple different therapeutic formats have been engineered, including multimeric binders and Fc fusion proteins. Subsequent site-specific attachment of highly potent toxins yielded homogeneous VNAR-based drug conjugates which demonstrated potent ROR1-dependant killing of selected cancer cell-lines in vitro with IC50 values in the picomolar range. In a series of in vivo studies, VNAR-hFc fusions conjugated with novel linker payloads were well tolerated in mice and showed significant anti-tumor activity in mouse xenograft models of cancer, including complete and sustained tumour regressions in a patient-derived xenograft (PDX) model of triple negative breast cancer. Lead VNAR-hFc conjugates have been successfully ‘humanized' guided by de novo structural biology. These engineered VNAR-hFc drug conjugates represent exciting new candidates for the treatment of a variety of both solid tumor and haematological cancer indications. Additionally, bi-paratopic and bi-specific ROR1 binders have been generated which fully leverage the modular design of VNAR-based therapeutics. These provide second generation drug conjugates which can be tailored to specific additional therapeutic applications, further extending the applicability of this approach.

Citation Format: Graham Cotton, Jennifer Thom, Paul Trumper, Andrei Kamenski, Stacey Bell, Mark Wappett, Caroline Barelle, Marina Kovaleva, Alicia Campion, Elisa Persiani, Andrew Porter, Estelle McLean, Aidan McCann, Chiara Saladino, Aaron Cranston, Tim Harrison. Exploiting the properties of VNAR domains for the development of novel efficacious protein drug conjugates targeting the oncofetal protein ROR1 [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 538.

Determination of Nitrogen Solubility in Dilute Pepsin Hydrochloric Acid Solution of Fishmeal: Interlaboratory Study

A revised method to determine solubility of nitrogen in dilute pepsin, using 0.0002% pepsin in place of 0.2% in AOAC Official Method 971.09, was tested in 16 laboratories with 12 samples of fishmeal. Results were calculated according to 2 procedures: AOAC Official Method 971.09 and a method described in 1964 by researchers at the Torry Research Station (Aberdeen, Scotland), and generally referred to as the modified Torry method. Variations in the method of shaking and source of pepsin were also investigated. Pepsin solubility values were lower and more variable when calculated by the Torry procedure. The method of shaking apparently affected the result when calculated according to the Torry but not the AOAC method. The source of pepsin had no significant effect on between-laboratory variability, but a comparison of the 2 main sources within one laboratory resulted in highly significant differences. Based on this study, the International Fishmeal and Fish Oil Organization has adopted this new method, using 0.0002% pepsin but keeping the AOAC method of calculation. The type of shaker and source of pepsin are recommended but are not mandatory. The repeatability and reproducibility limits of this new method are 1.6 and 3.3% units of solubility, respectively.

Abstract 222: Novel protein drug conjugates targeting ROR1 through the development and exploitation of a drug discovery platform based on small, engineered VNAR domains

Whilst antibody drug conjugates (ADCs) have been successfully used to target highly potent cytotoxic agents to tumours, there is a continued emphasis on developing technologies for improving the therapeutic effectiveness of this class of agents. The vast majority of ADCs that have entered the clinic have been based on large intact immunoglobulins, however, there is significant interest in exploiting small protein domains as the payload delivery vehicle. These offer a number of potential benefits over full length antibodies including increased tumour penetration, amenability to protein engineering and site-specific conjugation, and improved tolerability. To this end, we have developed a therapeutics platform based on shark Variable New Antigen Receptor (VNAR) proteins. Shark VNAR domains are the smallest naturally occurring antigen binding domain (~11 kDa), with a binding mechanism distinct from traditional antibodies. Here we report the application of this platform to the development of homogenous VNAR-drug conjugates targeting the onco-embryonic receptor tyrosine kinase ROR1.

ROR1 expression has been observed across a broad range of solid tumours and haematological malignancies, and is reported to correlate with poor clinical outcome for a number of cancer indications, but is largely absent from normal adult tissue. As such, the expression pattern of ROR1, coupled with its functional role in tumourogenesis and disease progression, make it an attractive PDC target. Using a combination of direct immunisation and synthetic VNAR library screening, we have generated high affinity binders to the extracellular domain of ROR1 which show species cross-reactivity, do not bind the closely related family member ROR2, and can target distinct non-overlapping regions of the protein. By exploiting the ability of VNAR domains to be flexibly reformatted, the lead sequences have been configured as a series of bivalent Fc fusions, VNAR multimers and novel bi-paratopic binders, and constructs identified that show further enhanced binding to ROR1 and which can induce internalisation and lysosomal trafficking in ROR1 expressing cancer cell-lines. Subsequent attachment of highly potent DNA-damaging cytotoxic payloads yielded homogenous VNAR-drug conjugates which demonstrated extremely potent (sub-nanomolar) in vitro cytotoxicity against selected cancer cell-lines in a receptor mediated fashion. Studies to assess the in vivo efficacy of these conjugates are in progress. These ROR1 VNAR constructs have also been successfully fused to sdAbs and scFv directed to other cell-surface protein targets, demonstrating the power of the platform and opening the way for novel bi-specific approaches for targeting both solid and haematological tumours.

Citation Format: Graham Cotton, Jennifer Thom, Paul Trumper, Stacey Bell, Andrei Kamenski, Mark Wappett, Caroline Barelle, Marina Kovaleva, John Steven, Andy Porter, Estelle McLean, Chiara Saladino, Aidan McCann, Aaron Cranston, Tim Harrison. Novel protein drug conjugates targeting ROR1 through the development and exploitation of a drug discovery platform based on small, engineered VNAR domains [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 222.

A Comparative Study of Fluorescence Assays in Screening for BRD4

Fluorescence assay technologies are commonly used in high-throughput screening because of their sensitivity and ease of use. Different technologies have their characteristics and the rationale for choosing one over the other can differ between projects because of factors such as availability of reagents, assay performance, and cost. Another important factor to consider is the assay susceptibility to artifacts, which is almost as important as the ability of the assay to pick up active compounds. Spending time and money on false positives or missing the opportunity to build chemistry around false negatives is something that every drug project tries to avoid. We used a BET family Bromodomain, BRD4(1), to explore the outcome of a screening campaign using three fluorescent assay technologies as primary assays. A diverse 7,038 compound set was screened in fluorescence lifetime, fluorescence polarization, and homogeneous time-resolved fluorescence to look at primary hit rates, compound overlap, and hit confirmation rates. The results show a difference between the fluorescence assay technologies with three separate hit lists and some overlap. The confirmed hits from each assay were further evaluated for translation into cells (NanoBRET™). Most of the actives confirmed in cells originated from compounds that overlapped between the assays. In addition, a well-annotated set of compounds with undesirable mechanism of inhibition was screened against BRD4(1) to compare the ability to discriminate true hits from artifact compounds. The results indicate a difference between the assays in their ability to generate false positives and negatives.

Single-Domain Antibody-Functionalized pH-Responsive Amphiphilic Block Copolymer Nanoparticles for Epidermal Growth Factor Receptor Targeted Cancer Therapy

Biocompatible antibody-nanoparticle conjugates have attracted interest as anticancer agents due to their potential to selectively target therapeutic agents at disease sites. However, new formulation and conjugation approaches are urgently needed to improve their uniformity for clinical applications. Here, a pH-responsive benzaldehyde-functionalized poly[oligo(ethylene glycol) methacrylate-st-para-formyl phenyl methacrylate]-b-poly[2-(diisopropyl)aminoethyl methacrylate] [P(OEGMA-st-pFPMA)-b-PDPA] block copolymer, prepared by reversible addition-fragmentation chain transfer polymerization, produced PEGylated nanoparticles (pH ∼ 7.4) by a single emulsion-solvent evaporation formulation approach. Efficient site-specific attachment of an aminooxy-functionalized anti-EGFR single-domain antibody (sdAb) on these benzaldehyde-decorated nanoparticles is achieved by oxime bond formation. These nanoconjugates can specifically bind EGFR (modified ELISA) and have enhanced uptake over nonfunctionalized controls in EGFR-positive HeLa cells. Encapsulation of rhodamine 6G dye and its dispersion upon cellular uptake, consistent with nanoparticle stability loss at pH < 5.7, prove their ability to facilitate triggered release in endosomal compartments and highlight their potential for use as next-generation antibody-drug nanoconjugates for therapeutic drug delivery.

Abstract LB-054: FKBPL as a novel therapeutic target and prognostic biomarker in high grade serous ovarian cancer

FKBPL is a secreted protein with well-established anti-angiogenic and anti-cancer stem cell activity. A novel therapeutic peptide, ALM201, derived from this protein has successfully completed a phase I clinical trial and was granted orphan drug status, by the FDA, for the treatment of ovarian cancer. Ovarian cancer is the most lethal gynecological cancer and there are no prognostic biomarkers currently used in the clinic. It is associated with a high incidence of recurrent chemo-resistant disease and this has been attributed to a treatment-resistant subpopulation of CD44+ cancer stem cells (CSCs). Previously, we presented evidence that CD44 is a potential target of ALM201 and here, for the first time, we investigate its ability to target both angiogenesis and CSCs in HGSOC. Tumorsphere and flow cytometry assays demonstrated that ALM201 is effective at reducing CSCs in a range of HGSOC cell lines and primary patient samples in vitro. Clonogenic assays demonstrated that ALM201 is not cytotoxic, but rather mediates ovarian CSC differentiation. In vitro, ALM201 displayed potent anti-CSC activity in the HGSOC cell line, OVCAR3. However, OVCAR3 tumor xenografts are not dependent on angiogenesis for their growth and therefore ALM201 did not elicit a strong response in this model. Furthermore, OVCAR3 xenografts dramatically upregulated the inflammatory cytokines IL-6 and IL-8, which is consistent with the lack of anti-CSC activity of ALM201 in vivo compared to in vitro. In contrast, treatment of highly angiogenic Kuramochi tumor xenografts, another HGSOC cell line, resulted in a statistically significant delay in both tumor growth and tumor initiation. This was associated with disruption of the CD31+ vascular network and a 10 fold decrease in the CSC population. Finally, using HGSOC tissue microarrays we demonstrated that high endogenous expression of FKBPL correlated with increased progression free interval; indicating the potential for FKBPL to be used as a prognostic biomarker in HGSOC. HGSOC cell lines display marked differences in tumor vascularisation in vivo. ALM201, a peptide fragment of FKBPL, has potent anti-CSC and anti-angiogenic activity in an HGSOC xenograft which is dependent on angiogenesis for growth; an important finding for the clinical development of ALM201. Our data also strongly suggest that FKBPL is a potential novel prognostic biomarker in HGSOC, supporting its endogenous anti-tumor activity.

Citation Format: Stephanie Annett, Gillian Moore, Amy Short, Neermeen Moustafa, Sudipto Das, Darran O'Connor, Cian McCrudden, Adrien Kissenpfenning, Laura Nelson, Ian Harley, Ken Arthur, Anita Yakkundi, Glen McCluggage, Andrea Marshall, Fiona Furlong, Helen O. McCarthy, Graham Cotton, Timothy Harrison, Lana McClements, Tracy Robson. FKBPL as a novel therapeutic target and prognostic biomarker in high grade serous ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr LB-054.

Chemokines as novel and versatile reagents for flow cytometry and cell sorting

Cell therapy regimens are frequently compromised by low-efficiency cell homing to therapeutic niches. Improvements in this regard would enhance effectiveness of clinically applicable cell therapy. The major regulators of tissue-specific cellular migration are chemokines, and therefore selection of therapeutic cellular populations for appropriate chemokine receptor expression would enhance tissue-homing competence. A number of practical considerations preclude the use of Abs in this context, and alternative approaches are required. In this study, we demonstrate that appropriately labeled chemokines are at least as effective in detecting their cognate receptors as commercially available Abs. We also demonstrate the utility of biotinylated chemokines as cell-sorting reagents. Specifically, we demonstrate, in the context of CCR7 (essential for lymph node homing of leukocytes), the ability of biotinylated CCL19 with magnetic bead sorting to enrich for CCR7-expressing cells. The sorted cells demonstrate improved CCR7 responsiveness and lymph node-homing capability, and the sorting is effective for both T cells and dendritic cells. Importantly, the ability of chemokines to detect CCR7, and sort for CCR7 positivity, crosses species being effective on murine and human cells. This novel approach to cell sorting is therefore inexpensive, versatile, and applicable to numerous cell therapy contexts. We propose that this represents a significant technological advance with important therapeutic implications.

Treatment of inflammatory bowel disease by chemokine receptor-targeted leukapheresis

Leukapheresis removes circulating leukocytes en route to the target organ. Hitherto unspecific matrixes have been used to remove leukocytes in inflammatory bowel disease (IBD). This report describes a novel selective leukapheresis column based on chemokine-chemokine receptor interaction. We found an increased expression of the gut homing chemokine receptor CCR9 on CD14(+) monocytes and on CD3(+) T lymphocytes from IBD patients. Biologically active CCL25 was coupled to a Sepharose matrix and demonstrated to selectively remove CCR9-expressing cells leaving other cell populations largely unaffected. A patient with active ulcerative colitis, was subjected to CCL25-column leukapheresis. Four days after treatment, he experienced clinical improvement and stable disease improvement ensued. The study illustrates that specific cells can be targeted using high affinity interactions, i.e., CCL25-CCR9 interactions to remove pathogenic gut-homing cells. Leukapheresis using the bCCL25 column should be investigated in a clinical phase I trial of patients with inflammatory bowel disease.

Abstract 3288: The anti-tumour efficacy of the novel peptide inhibitor of angiogenesis ALM-201

Neovascularization is critical to tumour growth and metastasis and this has led to the development of a number of marketed anti-angiogenic agents which target VEGF/VEGFR2 receptors, for clinical use in specific types of cancer. However, incomplete responses and/or resistance to these therapies has highlighted the need for new agents targeting alternative pathways. Here we describe the characterisation of a novel peptide derived from the natural protein FKBP-like binding protein (FKBPL), which has extremely potent anti-angiogenic activity, is very effective in mouse xenograft models at low doses, and exerts its effects through microtubule binding using CD44 as a cell-entry mechanism.

ALM-201 has been profiled in a range of human microvascular endothelial cell (HMEC-1) assays and potently inhibited migration, tubule formation and microvessel formation in vitro and in vivo. Although the peptide has a marked effect on migration, ALM-201 does not inhibit proliferation in a range of growth factor stimulated proliferation assays. Importantly, there is a significant disconnect between the pharmacokinetic and pharmacodynamic profiles of ALM-201 which allows for 3 q.d. dosing in mouse xenograft models. The peptide is well tolerated with no signs of toxicity observed in mouse xenograft models up to 80 days of dosing. The mechanism by which ALM-201 inhibits angiogenesis involves the cell surface receptor CD44, as determined by siRNA depletion of the receptor in migration assays. Furthermore, the peptide potently inhibits microtubule assembly and downstream signalling, thus promoting the anti-migratory phenotype.

In summary, ALM-201 is a novel, targeted microtubule binding agent which exhibits potent anti-angiogenic activity in vitro and in vivo. Pre-clinical development is in progress with a Phase 1 clinical study planned for 2011.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3288. doi:10.1158/1538-7445.AM2011-3288

FKBPL and peptide derivatives: novel biological agents that inhibit angiogenesis by a CD44-dependent mechanism

PURPOSE

Antiangiogenic therapies can be an important adjunct to the management of many malignancies. Here we investigated a novel protein, FKBPL, and peptide derivative for their antiangiogenic activity and mechanism of action.

EXPERIMENTAL DESIGN

Recombinant FKBPL (rFKBPL) and its peptide derivative were assessed in a range of human microvascular endothelial cell (HMEC-1) assays in vitro. Their ability to inhibit proliferation, migration, and Matrigel-dependent tubule formation was determined. They were further evaluated in an ex vivo rat model of neovascularization and in two in vivo mouse models of angiogenesis, that is, the sponge implantation and the intravital microscopy models. Antitumor efficacy was determined in two human tumor xenograft models grown in severe compromised immunodeficient (SCID) mice. Finally, the dependence of peptide on CD44 was determined using a CD44-targeted siRNA approach or in cell lines of differing CD44 status.

RESULTS

rFKBPL inhibited endothelial cell migration, tubule formation, and microvessel formation in vitro and in vivo. The region responsible for FKBPL's antiangiogenic activity was identified, and a 24-amino acid peptide (AD-01) spanning this sequence was synthesized. It was potently antiangiogenic and inhibited growth in two human tumor xenograft models (DU145 and MDA-231) when administered systemically, either on its own or in combination with docetaxel. The antiangiogenic activity of FKBPL and AD-01 was dependent on the cell-surface receptor CD44, and signaling downstream of this receptor promoted an antimigratory phenotype.

CONCLUSION

FKBPL and its peptide derivative AD-01 have potent antiangiogenic activity. Thus, these agents offer the potential of an attractive new approach to antiangiogenic therapy.

Activation of the focal adhesion kinase signaling pathway by structural alterations in the carboxyl-terminal region of c-Crk II

The Crk II adaptor protein encodes an SH2/SH3-domain containing adaptor protein with an SH2-SH3-SH3 domain structure that transmits signals from tyrosine kinases. The two SH3 domains are separated by a 54 amino acid linker region, whose length is highly conserved in xenopus, chicken, and mamalian Crk II proteins. To gain a better understanding into the role of the C-terminal region of Crk, we generated a series of C-terminal SH3 domain and SH3 linker mutants and examined their role in tyrosine kinase pathways. Expression of point mutations in the C-terminal SH3 domain (W276K Crk), at the tyrosine phosphorylation site (Y222F Crk II), or truncation of the entire C-terminus (Crk I or Crk Delta242), all increased c-Abl binding to the N-terminal SH3 domain of Crk and, where relevant, increased Tyr(222) phosphorylation. Deletion analysis of c-Crk II also revealed the presence of a C-terminal segment important for trans-activation of FAK. Such mutants, Crk Delta255 or Crk Delta242 Extended Linker (Crk Delta242([EL])), characterized by a disruption in the SH3 linker/C-terminal SH3 boundary, induced robust hyperphosphorylation of focal adhesion kinase (FAK) on Tyr(397), hyperphosphorylation of focal adhesion proteins p130(cas) and paxillin and increased focal adhesion formation in NIH3T3 cells. The effects of Crk Delta242([EL]) could be abrogated by co-expression of dominant negative c-Src or the protein tyrosine phosphatase PTP-PEST, but not by dominant negative Abl. Our results suggest that the C-terminal region of Crk contains negative regulatory elements important for both Abl and FAK dependent signal pathways, and offers a paradigm for an autoinhibitory region in the SH3 linker/C-terminal SH3 domain.

Laser-assisted angioplasty for arterial occlusion of the lower limb: initial results and follow-up

A flashlamp-pumped pulsed dye laser operating at either 480 or 504 nm, coupled to an integral ball-tipped optical fibre, was used to recanalize occluded lower limb arteries. All channels created by the laser were augmented with balloon dilatation. We have treated 78 limbs in 71 patients; 46 limbs (59 per cent) had rest pain and 22 (48 per cent) of these had tissue loss. The median occlusion length was 18 (range 0.5-58) cm. Technical success was achieved in 58 limbs (74 per cent) with clinical success in 46 (59 per cent). Success rates fell with increasing length of occlusion. Two patients died in the perioperative period. A subgroup of 22 patients with marked discrete arterial calcification had a lower technical success rate than the subgroup without calcification (50 per cent versus 84 per cent, P less than 0.01). Both subgroups displayed a similar pattern of reclosure during follow-up. The cumulative patency rate after technical success was 67 per cent at 6 months and 45 per cent at 12 months. Forty-six (59 per cent) limbs avoided bypass surgery or amputation. Laser-assisted angioplasty may offer an alternative to femoropopliteal bypass, although the former procedure is not as durable.

Biologically effective ultraviolet radiation: surface measurements in the United States, 1974 to 1985

Recent reports of stratospheric ozone depletion have prompted concerns about the levels of solar ultraviolet radiation that reach the earth's surface. Since 1974 a network of ground-level monitoring stations in the United States has tracked measurements of biologically effective ultraviolet radiation (UVB, 290 to 330 nanometers). The fact that no increases of UVB have been detected at ground levels from 1974 to 1985 suggests that meteorological, climatic, and environmental factors in the troposphere may play a greater role in attenuating UVB radiation than was previously suspected.

The effect of proteolytic degradation of plasma fibronectin on the responses of functional and immunometric assays for intact fibronectin

Numerous studies have been made into the nature and importance of altered levels of plasma fibronectin seen in a range of clinical disorders. However, fibronectin is highly sensitive to the proteolytic degradation which may accompany some of these conditions. The influence of such degradation on the assays used is frequently unknown. We have investigated the effects of controlled protease degradation on the responses of an electroimmuno and a functional assay, using purified fibronectin. Tryptic digestion influenced the assays more than thrombin, in relation to the degree of breakdown. Both enzymes reduced the functional (gelatin-binding) activity whilst tryptic cleavage increased the apparent concentration by electroimmunoassay. The findings demonstrate that certain assays may be inappropriate for those clinical conditions where levels of intact fibronectin are of most interest. It is also necessary, then, to determine the degree of fibronectin breakdown when measuring pathological levels.