Treat-and-Extend versus Monthly Regimen in Neovascular Age-Related Macular Degeneration: Results with Ranibizumab from the TREND Study.

PURPOSE: To evaluate the efficacy and safety of ranibizumab 0.5 mg treat-and-extend (T&E) versus monthly regimens in patients with neovascular age-related macular degeneration (nAMD) from the TReat and extEND (TREND) study. DESIGN: A 12-month phase 3b visual acuity (VA) assessor-masked, multicenter, randomized, interventional study. PARTICIPANTS: Six hundred fifty patients. METHODS: Treatment-naïve nAMD patients (age, ≥50 years) were randomized 1:1 to receive either a ranibizumab 0.5 mg T&E (n = 323) or monthly (n = 327) regimen. MAIN OUTCOMES MEASURES: The primary objective was to show noninferiority of ranibizumab 0.5 mg T&E versus monthly regimen, as assessed by the change in best-corrected VA (BCVA) from baseline to the end of the study. Secondary objectives included change in retinal central subfield thickness (CSFT) from baseline to the end of study, treatment exposure, and safety. RESULTS: Overall, 89.8% (T&E) and 90.2% (monthly) of patients completed the study. Patient demographic and baseline characteristics were well balanced between the 2 treatment groups. The T&E regimen was noninferior (P < 0.001) to the monthly regimen, with a least squares mean BCVA change from baseline of 6.2 versus 8.1 letters to the end of study, respectively. In both treatment groups, most BCVA improvements occurred during the first 6 months and were maintained until the end of the study. The mean change in CSFT from baseline to the end of study was -169.2 µm and -173.3 µm in the T&E and monthly groups, respectively. Fewer injections were required in patients receiving the T&E (8.7) versus monthly (11.1) regimen, with mean number of postbaseline visits of 8.9 and 11.2, respectively. Types and rates of adverse events were comparable between the treatment groups. CONCLUSIONS: Ranibizumab 0.5 mg administered according to a T&E regimen was statistically noninferior and clinically comparable with a monthly regimen in improving VA from baseline to the end of study. No new safety signals for ranibizumab were identified.

Efficacy and Safety of Ranibizumab With or Without Verteporfin Photodynamic Therapy for Polypoidal Choroidal Vasculopathy: A Randomized Clinical Trial.

Importance: Polypoidal choroidal vasculopathy (PCV) is a common subtype of exudative age-related macular degeneration among Asian individuals. To our knowledge, there are no large randomized clinical trials to evaluate intravitreal ranibizumab, with and without verteporfin photodynamic therapy (vPDT), for the treatment of PCV. Objective: To compare the efficacy and safety of combination therapy of ranibizumab and vPDT with ranibizumab monotherapy in PCV. Design, Setting, and Participants: A double-masked, multicenter randomized clinical trial of 322 Asian participants with symptomatic macular PCV confirmed by the Central Reading Center using indocyanine green angiography was conducted between August 7, 2013, and March 2, 2017. Interventions: Participants were randomized 1:1 to ranibizumab, 0.5 mg, and vPDT (n = 168; combination therapy group) or ranibizumab, 0.5 mg, and sham PDT (n = 154; monotherapy group). All participants received 3 consecutive monthly ranibizumab injections, followed by a pro re nata regimen. Participants also received vPDT/sham PDT on day 1, followed by a pro re nata regimen based on the presence of active polypoidal lesions. Main Outcomes and Measures: Step 1 assessed whether combination therapy was noninferior (5-letter margin) to monotherapy for change in best-corrected visual acuity from baseline and superior in complete polyp regression. If noninferiority was established, step 2 assessed whether combination therapy was superior to monotherapy measured by best-corrected visual acuity change at month 12. Results: Baseline demographics of the 322 participants were comparable between the treatment groups. Mean (SD) age of the patients was 68.1 (8.8) years, and overall, 69.9% of the patients were men. At baseline, the overall mean best-corrected visual acuity and mean central subfield thickness were 61.1 letters and 413.3 µm, respectively. At 12 months, mean improvement from baseline was 8.3 letters with combination therapy vs 5.1 letters with monotherapy (mean difference, 3.2 letters; 95% CI, 0.4-6.1), indicating that combination therapy met the predefined criterion for noninferiority as well as being superior to monotherapy (P = .01). Combination therapy was also superior to monotherapy in achieving complete polyp regression at month 12 (69.3% vs 34.7%; P < .001). Over 12 months, the combination therapy group received a median of 4.0 ranibizumab injections compared with 7.0 in the monotherapy group. Vitreous hemorrhage was the only ocular serious adverse event (combination therapy group, 1 [0.6%]; monotherapy group, 3 [2.0%]). Conclusions and Relevance: After 12 months, combination therapy of ranibizumab plus vPDT was not only noninferior but also superior to ranibizumab monotherapy in best-corrected visual acuity and superior in complete polyp regression while requiring fewer injections. Combination therapy should be considered for eyes with PCV. Trial Registration: clinicaltrials.gov Identifier: NCT01846273.

Mathematical Modeling of the Dynamics of Shoot-Root Interactions and Resource Partitioning in Plant Growth.

Plants are highly plastic in their potential to adapt to changing environmental conditions. For example, they can selectively promote the relative growth of the root and the shoot in response to limiting supply of mineral nutrients and light, respectively, a phenomenon that is referred to as balanced growth or functional equilibrium. To gain insight into the regulatory network that controls this phenomenon, we took a systems biology approach that combines experimental work with mathematical modeling. We developed a mathematical model representing the activities of the root (nutrient and water uptake) and the shoot (photosynthesis), and their interactions through the exchange of the substrates sugar and phosphate (Pi). The model has been calibrated and validated with two independent experimental data sets obtained with Petunia hybrida. It involves a realistic environment with a day-and-night cycle, which necessitated the introduction of a transitory carbohydrate storage pool and an endogenous clock for coordination of metabolism with the environment. Our main goal was to grasp the dynamic adaptation of shoot:root ratio as a result of changes in light and Pi supply. The results of our study are in agreement with balanced growth hypothesis, suggesting that plants maintain a functional equilibrium between shoot and root activity based on differential growth of these two compartments. Furthermore, our results indicate that resource partitioning can be understood as the emergent property of many local physiological processes in the shoot and the root without explicit partitioning functions. Based on its encouraging predictive power, the model will be further developed as a tool to analyze resource partitioning in shoot and root crops.

Self-organization of plant vascular systems: claims and counter-claims about the flux-based auxin transport model.

The plant hormone auxin plays a central role in growth and morphogenesis. In shoot apical meristems, auxin flux is polarized through its interplay with PIN proteins. Concentration-based mathematical models of the flux can explain some aspects of phyllotaxis for the L1 surface layer, where auxin accumulation points act as sinks and develop into primordia. The picture differs in the interior of the meristem, where the primordia act as auxin sources, leading to the initiation of the vascular system. Self-organization of the auxin flux involves large numbers of molecules and is difficult to treat by intuitive reasoning alone; mathematical models are therefore vital to understand these phenomena. We consider a leading computational model based on the so-called flux hypothesis. This model has been criticized and extended in various ways. One of the basic counter-arguments is that simulations yield auxin concentrations inside canals that are lower than those seen experimentally. Contrary to what is claimed in the literature, we show that the model can lead to higher concentrations within canals for significant parameter regimes. We then study the model in the usual case where the response function Φ defining the model is quadratic and unbounded, and show that the steady state vascular patterns are formed of loopless directed trees. Moreover, we show that PIN concentrations can diverge in finite time, thus explaining why previous simulation studies introduced cut-offs which force the system to have bounded PIN concentrations. Hence, contrary to previous claims, extreme PIN concentrations are not due to numerical problems but are intrinsic to the model. On the other hand, we show that PIN concentrations remain bounded for bounded Φ, and simulations show that in this case, loops can emerge at steady state.