Runway math when your milestone is a readout

Runway in biotech is not a number, it is a relationship between three dates: the date your key data reads out, the date you can close a financing on that data, and the date cash reaches zero. A company with eighteen months of runway and a readout in month twenty is in trouble. A company with fourteen months of runway and a readout in month eight is in a strong position. Simple cash over burn hides that difference entirely.

The three numbers the board is actually asking for

1. Months to readout. When will the data that changes your valuation be available, and what is the probability weighted range around that date given enrollment to date?
2. Cash at readout. How much will be in the bank on that date under the current operating plan?
3. Runway after readout. How many months does that cash buy after the data arrives, which is the time you have to run a process, negotiate, and close?

The third number is the one to protect. A financing process on positive data takes four to six months from first meeting to money in the bank, longer in a difficult market. If runway after readout is under six months, investors know you have to close, and the price reflects it. Nine months of cushion is the target most experienced boards use. Twelve is comfortable.

Build the model from the trial, not from the P&L

A runway model that starts from last quarter's burn and extrapolates will miss the shape of clinical spend. Trials are lumpy: heavy in startup, peaking during enrollment, tapering through follow up and database lock. Build the forecast bottom up from the clinical budget with the same cost drivers used for accruals, layer in CMC batches on their actual scheduled months, and add the hiring plan by start date. Then apply the fixed cost base. The result will show months where burn is double the average, and those months need to be visible before they arrive.

Model the slip explicitly

Enrollment slips. Every month of delay does two things at once: it pushes the readout date out and it extends the period of peak clinical spend. In most models a three month enrollment delay reduces runway after readout by five to six months, not three, because the burn during the delay is at the trial's highest rate. Build a delay input into the model and show the board the runway after readout at zero, three, and six months of slip. If the six month case leaves you short, the conversation about a bridge or a scope reduction should happen now, while you have leverage.

The levers, in the order to pull them

• Sequence, do not cut. Delaying the start of a second program or a CMC scale up batch by a quarter often preserves the lead program's timeline while moving meaningful cash past the readout.
• Time hires to the data. Commercial, quality, and second program hires planned for before the readout can usually wait until after it without harming the trial.
• Non dilutive money. Grants, foundation funding, and tax credits are slow but real. A state research credit or a federal grant filed twelve months early can add a month of runway at no cost to the cap table.
• Venture debt, carefully. It works when drawn before the readout and sized so that covenants and the interest only period run past the financing. It fails when the draw is conditional on data you do not yet have.
• A bridge from insiders. Existing investors would rather extend than watch you raise from necessity. Ask early, while the ask is small.

What to show every month

One page. The trial timeline with the projected readout and the slip range. The cash curve with the readout month marked. The three numbers: months to readout, cash at readout, runway after readout, each against the same numbers from last month. When any of the three moves, say why in one sentence. A board that sees this every month never gets surprised, and a CEO who has it never walks into a financing without knowing exactly how much time is on the clock.