The US rules that make it very hard for legal drug makers to obtain US import licences are what enabled that guy to raise the price of a drug by over 50 times. Notice that wasn't illegal; he has been arrested for possible securities fraud, not for price gouging.
Pinsent Mason seem to be leaving is with the implication that if we leave the EU, the NHS will suffer as the pharma companies use the absence of EU competition law to raise drug prices. That absence of competition law will also allow other companies to create monopolies. Nice for friends of the Conservatives.