md`--- ## Example - Drug development production chain In this example we consider the drug development production chain. In a first stage, the drug substance (DS) is produced with a given concentration of the active pharmaceutical ingredient (API), e.g. 100mg/ml. In a second stage, drug substance is formulated into some drug products (DP) of a given form (e.g. vials). Multiple concentrations of the API are considered, e.g. 300mg/ml, 200mg/ml, 100mg/ml and 0mg/ml (placebo). Each one is treated as a different product of the DP stage. Comparator product (marketed product) is also considered as a different DP product. In a third stage, drug products are packaged into investigational medicinal products (IMP) which form the kits that will be dispensed to the patients enrolled in the clinical trials (e.g. a box containing a certain number of vials). The design of the kits depends in the clinical trial. Again, each design is treated as a different product of the IMP stage. Integrated device (DV) is considered as well (e.g. syringes) as a specific production stage. In this example, most of the demands represent the clinical trials that are supplied by the production chain. Demands can also be supplied by product from a non-final (intermediate) stage, e.g. SDP 01 in the example. The bill of materials for one specific product can include multiple upstream products (for example lot IMP014 of product IMP 2xACT200 requires two different upstream products: DP ACT200 and DV MON). In such case, the input flows from each required product overlap. In some other cases, the required quantity of one upstream product may come from multiple lots of that same product. In such case, the input flows from each lot stack, as show for DP006 which consumes DS taken from two lots: DS001 and DS002. Overlaping and stacking of input flows may also occur together as shown for lot IMP015 which consumes quantities from two lots of product DV MON (flows are stacked) and quantity from one lot of the other required product DP ACT200 (flow overlaps). Lot can be only partially allocated, as for example DS002. The unallocated fraction is represented by the empty part of the bar. In this example, unallocated part corresponds to quantities taken for sampling and quantities lost due to product expiry. Lots are ordered vetically according to their production date, within each product group when grouping per product or over the full production stage otherwise. In this example coming from the pharmaceutical industry, exploring lot allocation flow allows to quickly visualize all possible usages of one given lot which is a great support for traceabilty. `