Most candidates prep for L.E.K. by collecting prompts. That is the wrong inventory. What the interviewer is scoring is a twenty-minute commercial diligence loop: size the opportunity, pressure-test one growth claim against an exhibit, then land a yes, no, or conditional yes with a number and a risk attached.
L.E.K. is built for that loop. The firm publicly runs commercial due diligence for private equity and claims more than $140 billion of life sciences deal support. Its interview-preparation page publishes three cases with no answers and six tips that end with "come up with an answer" while staying willing to rethink. After this piece you should be able to run one original L.E.K.-style case cold, then use the firm's own three prompts as scoring drills rather than as puzzles to memorize.
What L.E.K. actually tells you about the interview
As of 2026, About L.E.K. lists 27 offices, 2,300+ employees, and 2,000+ cases annually. That scale matters less than the shape of the work. Diligence and life sciences transaction support show up as named practices, not as footnotes.
The apply page is blunt about process: it "differs slightly by region" and includes "a mixture of experiential and case interviews (both quantitative and strategic cases are possible)." Treat any guide that invents a fixed global sequence of "two 30-minute cases then a 60-minute written" as folklore until your invitation confirms it. Round counts, written cases, and timing are office- and role-specific.
What you can trust from L.E.K. itself:
| Source | What it states | What it does not state |
|---|---|---|
| Interview preparation page | Three practice prompts; six in-case tips; prepare with workshops, news, and firm content | No answer keys; no official scoring rubric |
| Apply page | Regional variation; quantitative and strategic cases both possible | Exact round count, duration, or written-case format |
| PE / life sciences practice pages | CDD and deal support as core offerings | Which case prompts your office will use |
The practice implication. Spend your hours on estimate discipline, exhibit math, and a crisp recommendation. Do not spend them reverse-engineering a process L.E.K. refuses to standardize in public.
The diligence loop interviewers reward
In a typical first-round slot of roughly half an hour, I score the case more than the fit chat. Inside that case I am listening for four moves, in order:
- Restate the decision in one sentence (buy / enter / price / fix).
- Build a two- or three-branch tree that can kill the thesis, not a generic profitability MECE dump.
- Ask for the highest-value exhibit and do the arithmetic out loud with units attached.
- Commit, then name the one assumption that would flip you.
L.E.K.'s own tip six is the same instruction in softer language: commit, then update when new data arrives. Candidates who hedge until minute twenty-eight lose points even when their structure looks tidy.
Ned's rule. If your market size never becomes a denominator for a go-or-no-go, you practiced the wrong sport. At L.E.K. the estimate is the first draft of the recommendation, not a warm-up puzzle.
Mini-case: HelixPath US market entry (original)
Invented company, invented numbers, internally consistent. Cover the solution and give yourself three minutes to structure before you look.
Prompt. HelixPath is a European specialty pharma with a once-daily oral therapy for moderate-to-severe atopic dermatitis, approved in the EU. US Phase 3 is complete. Management wants a US launch in 24 months via a 120-person specialty sales force. Peak US sales guidance is $480M. A mid-market PE fund owns 40% of HelixPath and has asked you whether the US entry plan is commercially credible, and whether the fund should fund the launch or seek a partner.
Structure that earns the room. Three testable branches only:
- Is the addressable patient pool large enough to support $480M at a realistic price and share?
- Does the sales-force plan match the call points that actually write scripts?
- Is self-commercialization NPV-positive versus partnering, given cash and risk?
Ask for one exhibit first: diagnosed patients, treatment rates, and competitive share. Do not open with a seven-box "go-to-market framework."
Exhibit A (invented)
| Segment | US diagnosed patients (000s) | Currently treated (%) | Avg. net price / year ($) | Current branded share of treated (%) |
|---|---|---|---|---|
| Moderate | 1,800 | 35 | 18,000 | 55 |
| Severe | 420 | 70 | 32,000 | 80 |
| Mild (out of label) | 4,200 | 10 | 6,000 | 5 |
Math, stated as case assumptions
Start with on-label only. Mild is out of label; ignore it unless the interviewer invites expansion.
Treated moderate = 1,800k x 0.35 = 630k. Treated severe = 420k x 0.70 = 294k. Total treated on-label = 924k.
Assume HelixPath can take 12% of treated moderate and 18% of treated severe by year 5 (second-to-market oral, cleaner label than the leader on itch reduction). Patients = (630k x 0.12) + (294k x 0.18) = 75.6k + 52.9k = 128.5k.
Net price: assume a blended $22,000 after rebates (between moderate and severe anchors, weighted toward moderate volume). Peak revenue = 128.5k x $22,000 ≈ $2.83B if every patient stayed on therapy a full year. That is nonsense as a revenue number for a specialty oral with adherence drag. Apply persistence of 55% annualized patient-years: 128.5k x 0.55 x $22,000 ≈ $1.55B patient-year revenue at peak share. Still far above management's $480M.
So the issue is not "is the market big enough." The market is more than large enough. The issue is whether $480M is a conservative plan or a sandbagged number hiding a weak commercial engine.
Back into the implied patient-years at $480M: $480M / $22,000 ≈ 21.8k patient-years. At 55% persistence that is about 40k peak patients, or roughly 4.3% of the 924k treated pool. That is a thin share for a funded specialty launch, but believable if payers restrict or if the sales force cannot reach dermatology and allergist call points.
Sales-force check. 120 reps x 180 productive days x 8 calls/day = 172,800 calls/year. If each priority HCP needs 12 calls/year to stay productive, the force covers about 14,400 HCPs. Ask whether the priority list is 8,000 or 25,000. If it is 25,000, the plan under-covers by almost half and $480M becomes optimistic, not conservative.
Recommendation
Conditional yes on the market; no on funding a 120-rep self-launch at this plan quality. Fund a partnered US launch (co-promote or out-license with milestones) unless management can show (a) a priority HCP list under ~12,000, (b) payer research supporting the $22k net, and (c) a path to at least 6% treated share without doubling headcount. The diligence risk to name first is access and call-point coverage, not epidemiology. Epidemiology is fine; the commercial plan is the soft underbelly.
That is the loop: size, exhibit, recommendation with a flip condition. Run every L.E.K. practice case until that sequence is automatic.
How to use L.E.K.'s three official prompts
L.E.K. publishes three cases on its interview-preparation page: an aircraft brainteaser, Brewery Profits (two brewers, similar revenue, different profit volatility), and Large Pharma Co. (baldness pill: size and price). There are no official answers. The "Approaching the Case Interview" bullets under each prompt are the real exercise.
Use them this way, once each, timed:
| Official prompt | What to practice | Pass condition (Ned's bar) |
|---|---|---|
| Aircraft brainteaser | Single clock, endpoint discipline | You name the boundary cases before stating a number |
| Brewery Profits | Volatility with stable revenue | You isolate cost structure / operating leverage before listing "ideas" |
| Large Pharma Co. | Estimate as pricing input | Your price and revenue share one denominator; you flex one assumption aloud |
Do not "decode" them into memorized answers. Interviewers can smell a rehearsed 11-plane speech. They cannot smell a method you have rehearsed on different numbers.
If you want process and round design rather than practice material, use the L.E.K. case interview guide. For sizing mechanics in isolation, use market sizing practice.
A second prompt to run cold (PE commercial diligence)
Prompt. Meridian Dental is a 48-clinic dental platform. Trailing revenue $186M, EBITDA $28M (15%). A PE sponsor is bidding 11x EBITDA. Management claims same-clinic revenue growth of 7% next year. You get one clarifying question and then five minutes for a structure and a buy/pass lean.
What a strong clarifying question looks like. "Of the 7%, how many points are price versus visits versus mix, and how much of last year's growth came from clinics acquired mid-year?"
Lean (illustrative). At 11x, equity value is about $308M of enterprise value on $28M EBITDA before net debt. If same-clinic growth is mostly price (say 5 of 7 points) in a discretionary category, pass or rebid toward 9x unless churn and new-patient metrics are pristine. If growth is visits and the pipeline of de novo sites is contracted, diligence continues. The case is won or lost on growth quality, not on a generic "market attractive / company strong / risks" slide.
Practice this today
Run one full diligence loop out loud before you touch another framework PDF.
- Take the HelixPath case above cold: three minutes structure, eight minutes math, two minutes recommendation.
- Immediately run a scored structure or math drill on the exact skill that wobbled.
CoachNed keeps everything open for seven days with no card; then $120 for a recruiting season or $49 a month. The live voice case and the case library are the closest substitute for a partner across the table when you do not have one.
Frequently asked questions
Does L.E.K. publish official case answers?
No. The interview-preparation page gives three prompts and approach questions only. Treat third-party "solutions" as practice material, not as L.E.K. gospel.
Are L.E.K. cases interviewer-led or candidate-led?
L.E.K. does not publish a global label. In practice most offices run candidate-led cases where you drive the tree and request data, with quantitative and strategic flavors both possible per the apply page. Confirm the format on your invitation.
Should I practice life sciences and PE diligence specifically for L.E.K.?
Yes if you can. L.E.K. markets life sciences and commercial due diligence as core. Sector vocabulary is an edge; estimate discipline still matters more than jargon.
Is there a standard L.E.K. written case?
Not in the firm's public materials. Candidate reports of a written case in some final rounds are folklore until your office confirms packet length, output, and timing. Practice a timed slide recommendation anyway; the skill transfers.
How is CoachNed different from reading more L.E.K. prompts?
Reading prompts builds recognition. Scored reps build the diligence loop under time. CoachNed is independent and not affiliated with L.E.K. Consulting or any other firm named here.
Sources
- Interview Preparation | L.E.K. Consulting — three official case prompts and in-case tips. Checked 2026-09-24.
- Apply | L.E.K. Consulting — regional process variation; quantitative and strategic cases. Checked 2026-09-24.
- About L.E.K. | L.E.K. Consulting — 27 offices, 2,300+ employees, case volume. Checked 2026-09-24.
- Commercial Due Diligence | L.E.K. Consulting — PE CDD positioning and client questions. Checked 2026-09-24.
- Biotech and Pharmaceuticals | L.E.K. Consulting — life sciences transaction support claim ($140B+). Checked 2026-09-24.