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e15571 Background: Many patients with metastatic colorectal cancer (mCRC) that have failed standard first- and second-line therapies remain fit and eager for further treatment. Therapeutic options include two agents with proven but modest survival benefit, a clinical trial of an investigational agent, rechallenge with agents successfully used in earlier lines of treatment, or agents that have shown some activity in non-randomised phase II studies. Patient derived tumouroid (PDT) are self-organizing three-dimensional in vitro models cultured from a fresh tumour biopsy. They potentially represent a robust personalized model for real-time drug sensitivity testing to determine optimal anti-cancer therapies for individual patients. Methods: FORECAST-1 is an observational, non-randomized study to determine the feasibility of PDT based drug sensitivity screening for patients with mCRC that have failed at least two lines of therapy. Once established, PDTs undergo drug sensitivity screening including agents regorafenib, trifluridine/tipiracil (TAS102), oxaliplatin, irinotecan, 5-fluorouracil (5FU), erlotinib (a surrogate EGFR-inhibitor), gemcitabine, pemetrexed and temozolomide. Patients are treated at clinician discretion, with clinical response to be correlated with PDT response. Results: Since September 2020 we have enrolled 18 of a planned 30 patients, median age 55 years (range 44 – 81). 17 patients were ECOG 0-1. Four patients had received prior TAS102 treatment. Biopsies were obtained from liver (n = 6), soft tissue/peritoneal metastases (5), lung (2), lymph node (2), primary (1), brain (1) and bone (1). Drug sensitivity testing has been performed on seven PDTs at a median of 62 days from biopsy (range 42 – 128), one PDT culture has failed. A standardised reporting template has been developed. Treatments received by patients to date include TAS102 (n = 5), regorafenib (2), FOLFOX (3), FOLFIRI (1) FOLFIRI plus EGFR-inhibitor (1), capecitabine plus bevacizumab (1) and an immunotherapy-based clinical trial (1). Four patients did not receive further anti-cancer therapy post enrolment, and one patient is yet to commence further systemic therapy. Conclusions: Enrolment to this feasibility study has been rapid demonstrating this to be an area of clinical need. PDTs have been successfully established from a high proportion of patients, but with variable growth rates. Methods to accelerate PDT culture and drug testing are being pursued to increase the feasibility of a planned prospective study of PDT sensitivity informing patient management. Clinical trial information: ACTRN12620001353987.

Nicotine exposure during the fetal and neonatal periods (Developmental nicotine exposure, DNE) is associated with ineffective upper airway protective reflexes in infants. This could be explained by desensitized chemoreceptors and/or mechanoreceptors, diminished neuromuscular transmission or altered synaptic transmission among central neurons, as each of these systems depend in part on cholinergic signaling through nicotinic acetylcholine receptors (nAChRs). Here we showed that DNE blunts the response of the genioglossus muscle to nasal airway occlusion in lightly anesthetized rat pups. The genioglossus muscle helps keep the upper airway open and is innervated by hypoglossal motoneurons (XIIMNs). Experiments using the phrenic nerve-diaphragm preparation showed that DNE does not alter transmission across the neuromuscular junction. Accordingly, we used whole cell recordings from XIIMNs in brainstem slices to examine the influence of DNE on glutamatergic synaptic transmission under baseline conditions and in response to an acute nicotine challenge. DNE did not alter excitatory transmission under baseline conditions. Analysis of cumulative probability distributions revealed that acute nicotine challenge of P1-P2 preparations resulted in an increase in the frequency of nicotine-induced glutamatergic inputs to XIIMNs in both control and DNE. By contrast, P3-P5 DNE pups showed a decrease, rather than an increase in frequency. We suggest that this, together with previous studies showing that DNE is associated with a compensatory increase in inhibitory synaptic input to XIIMNs, leads to an excitatory-inhibitory imbalance. This imbalance may contribute to the blunting of airway protective reflexes observed in nicotine exposed animals and human infants. Significance statement The number one risk factor for sudden infant death (SIDS) is maternal smoking. While the use of nicotine delivery devices such as e-cigarettes is increasing among women of childbearing age, reflecting the belief that the use of nicotine alone is safer than tobacco, SIDS deaths are not decreasing, suggesting that nicotine is the link between maternal smoking and SIDS. Here we show that perinatal nicotine exposure alters a major motor pathway responsible for upper airway patency during sleep. We also introduce an animal model that is well suited to probing the mechanisms underlying the link between maternal nicotine consumption and SIDS, and a phenotype that nicely models key aspects of the events believed to give rise to SIDS.