Not a lawyer nor an executive but it's a common practice and also common for companies to file lawsuits for poaching to waste each others time and money. I've had to interview people off-site to avoid such troubles. One viable? tactic is to pay the employees well sometimes called golden hand-cuffs but competing with big pharma may be tough. Pre-IPO shares maybe but in a 5 person company the IPO could be too far out to keep them around. Company perks if you can afford it? Flexible hours, work from remote, good company laptops and so on. It could be worse. Your company could grow, become really successful and that big pharma may just want to take over your company using dirty tactics. Offering your customers the same products at 90% discount just long enough to put you under. Anything else I could suggest would be crossing out of the grey area.