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Question about drug pipeline case

I was looking at the solution for question 3 of this case: https://www.mckinsey.com/careers/interviewing/globapharm

It says that because value after Phase II trials must increase by $150m, and value otherwise is $540m, then Phase I + Phase II success rate must increase by 28% (150/540).

Can someone explain why this is? If lifetime profits after release are fixed at $1.2b, doesn't value after Phase II only depend on the success rate of Phase III and Phase IV? 

Why does the value increase of $150m after Phase II imply that Phase I + Phase II success rate must increase by 28%?

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Top answer
Hagen
Coach
on Mar 27, 2023
#1 recommended coach | >95% success rate | 8+ years consulting, 8+ years coaching and 7+ years interviewing experience

Hi there,

I think this is an interesting question that may be relevant for many people. I would be happy to share my thoughts on it:

  • Given that the expected value is calculated in the form of $vm * w% (phase I) * x% (phase II) * y% (phase III) = $zm, if the expected value after phase II needs to increase by 28%, then the product of w% (phase I) * x% (phase II) needs to increase by the same amount, which is the combined success rate of phases I and II.

If you would like a more detailed discussion on how to best prepare for your upcoming interviews, please don't hesitate to contact me directly.

Best,

Hagen

Ian
Coach
on Mar 27, 2023
Top US BCG / MBB Coach - 5,000 sessions |Tech, Platinion, Big 4 | 9/9 personal interviews passed | 95% candidate success

Hi there,

I'm sorry but I'm super confused by your question (the wording is really hard to follow).

Drug pipeline case math is notoriously tricky. I think this is where you are getting confused:

Remember that each stage success is independent of the previous phase.

So, for Phase II, only 40% of the drugs that already passed phase 1 make it through.

Therefore, if 100 drugs started, only 28 make it to phase 3.

100 times 70% success in phase 1 = 70 drugs. 

70 drugs times 40% success in phase 2 = 28 drugs.

28% is the % of drugs that will make it to phase 3

Anonymous A
on Mar 27, 2023
I understand that, I am specifically confused as to why the required increase in value after Phase 2 to break even on the investment means that combined Phase 1 + Phase 2 success rate must increase by the same % amount.
Emily
Coach
on Mar 27, 2023
Ex McKinsey EM & interviewer (5 yrs) USA & UK| Coached / interviewed 300 +|Free 15 min intro| Stanford MBA|Non-trad

Happy to help! I'll try my best to explain in writing but it might be worth a quick call if you're still confused. 

So in this case, a drug is being taken through from idea to being a successful, sellable drug. To do this it needs to go through a number of hoops, or ‘phases’. The numbers which go from bubble to bubble in green show the probability of getting through each phase. The client is not guaranteed the $1.2B - that's only if the drug gets through all the phases.

When you're looking at expected return on an investment where there is uncertainty like this, you multiply the expected return is by the probability of getting that return. This way you account for the uncertainty of not passing through all the stages.

So in this case, the client wants to know if they invest $150M into phase 2, if the success rate from phase 2 to phase 3 could increase enough to make the investment worthwhile. Therefore, you need to know what probability of the drug getting through all the stages needs to be to make the investment worthwile.

Currently, a drug has a 45% success rate of getting through phase 3 and filing (50%*90%). Given that, once a drug passes phase 2 it is ‘worth’ £1.2B * 45% = $540M. 

So if you've added an additional $150M into the costs, you need to make that back. So you need to increase your return to $540 + $150M = $690M; or an increase of $150M/$540M = 28%. 

Hope that makes sense, please let me know if it doesn't!

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