Merrimack Pharmaceuticals, Inc. (MACK)
MACK moved a median of 0.00% 30 minutes after news, and 0.00% by the close. How MACK actually reacts to news — the realized, point-in-time move the market made, measured across 41 labeled events over the last three years with zero look-ahead.
MACK’s median reaction, across the day.
| Horizon | Median | % positive | Events |
|---|---|---|---|
| 5-min | 0.00% | 40% | 38 |
| 30-min | 0.00% | 50% | 40 |
| 60-min | +0.10% | 65% | 40 |
| to close | 0.00% | 48% | 40 |
| Middle 50% of MACK reactions | -0.14% to +0.30% |
|---|---|
| Median reaction (30-min) | 0.00% |
| Measured reactions | 41 |
Half of all Merrimack Pharmaceuticals, Inc. news events land between -0.14% and +0.30% at 30 minutes.
Reaction stats as of 2026-09-21. Newest measured event . Reaction = percent move vs. the price at the news timestamp.
Email me when MACK moves on news.
One email per qualifying move — the headline, the measured reaction, and how it compares to MACK's baseline. Nothing else.
Recent MACK events, each with its measured reaction.
| Date | Headline | Event | Source | 5-min | To close |
|---|---|---|---|---|---|
| Form 15-12G MERRIMACK PHARMACEUTICAL | SEC filing · Form 15-12G | SEC EDGAR | — | — | |
| Form 10-Q MERRIMACK PHARMACEUTICAL For: Mar 31 | SEC filing · Form 10-Q | SEC EDGAR | -0.10% | -0.07% | |
| Form 25 MERRIMACK PHARMACEUTICAL | SEC filing · Form 25 | SEC EDGAR | +0.10% | -0.07% | |
| Form 8-K MERRIMACK PHARMACEUTICAL For: May 10 | SEC filing · Form 8-K | SEC EDGAR | +0.10% | -0.07% | |
| Merrimack Pharmaceuticals, Inc. Announces Stockholder Approval of Plan of Dissolution And Cash Liquidating Dividend Amount of $15.10 Per Share of Common Stock | Press release | Business Wire | +0.10% | -0.07% | |
| Form 8-K MERRIMACK PHARMACEUTICAL For: May 08 | SEC filing · Form 8-K | SEC EDGAR | +0.00% | -0.13% | |
| Form DEFA14A MERRIMACK PHARMACEUTICAL | SEC filing · Form DEFA14A | SEC EDGAR | +0.00% | -0.13% | |
| Merrimack Pharmaceuticals, Inc. Announces Anticipated Final Cash Dividend Amount of Initial Liquidating Distribution, Subject to Receipt of Stockholder Approval of Plan of Dissolution | Press release | Business Wire | +0.00% | -0.13% | |
| Form 8-K MERRIMACK PHARMACEUTICAL For: Apr 30 | SEC filing · Form 8-K | SEC EDGAR | +0.07% | +0.20% | |
| Form DEFA14A MERRIMACK PHARMACEUTICAL | SEC filing · Form DEFA14A | SEC EDGAR | +0.07% | +0.20% | |
| Merrimack Pharmaceuticals Announces Notification of Plan to Voluntary Delist Common Stock on NASDAQ Subject to Receipt of Stockholder Approval of Plan of Dissolution | Press release | Business Wire | +0.07% | +0.20% | |
| Form DEFR14A MERRIMACK PHARMACEUTICAL | SEC filing · Form DEFR14A | SEC EDGAR | +0.00% | +0.00% | |
| Form 8-K MERRIMACK PHARMACEUTICAL For: Mar 27 | SEC filing · Form 8-K | SEC EDGAR | +0.10% | +0.07% | |
| Form DEFA14A MERRIMACK PHARMACEUTICAL | SEC filing · Form DEFA14A | SEC EDGAR | +0.10% | +0.07% | |
| Merrimack Receives $225 Million Milestone Payment from Ipsen | Press release | Business Wire | +0.10% | +0.07% | |
| Form DEFA14A MERRIMACK PHARMACEUTICAL | SEC filing · Form DEFA14A | SEC EDGAR | +0.00% | -0.07% | |
| Form 10-K/A MERRIMACK PHARMACEUTICAL For: Dec 31 | SEC filing · Form 10-K | SEC EDGAR | +0.03% | +0.20% | |
| Form DEF 14A MERRIMACK PHARMACEUTICAL For: May 10 | SEC filing · Form DEF | SEC EDGAR | +0.03% | +0.20% | |
| Form 10-K MERRIMACK PHARMACEUTICAL For: Dec 31 | SEC filing · Form 10-K | SEC EDGAR | +0.00% | -0.41% | |
| Form 8-K MERRIMACK PHARMACEUTICAL For: Mar 07 | SEC filing · Form 8-K | SEC EDGAR | +0.00% | -0.41% | |
| Merrimack Reports Full Year 2023 Financial Results | Press release | Business Wire | +0.00% | -0.41% | |
| Form PRE 14A MERRIMACK PHARMACEUTICAL For: Mar 05 | SEC filing · Form PRE | SEC EDGAR | +0.00% | +0.14% | |
| Form 8-K MERRIMACK PHARMACEUTICAL For: Feb 13 | SEC filing · Form 8-K | SEC EDGAR | -0.54% | -0.74% | |
| Form DEFA14A MERRIMACK PHARMACEUTICAL | SEC filing · Form DEFA14A | SEC EDGAR | -0.54% | -0.74% | |
| Merrimack Reports Ipsen Announcement of Approval By The US FDA of Onivyde® (Irinotecan Liposome Injection) Plus 5 Fluorouracil/Leucovorin and Oxaliplatin (NALIRIFOX) as a First-Line Treatment for Metastatic Pancreatic Ductal Adenocarcinoma (mPDAC) | Press release | Business Wire | -0.54% | -0.74% | |
| Form 10-Q MERRIMACK PHARMACEUTICAL For: Sep 30 | SEC filing · Form 10-Q | SEC EDGAR | +0.00% | +0.81% | |
| Form 8-K MERRIMACK PHARMACEUTICAL For: Nov 02 | SEC filing · Form 8-K | SEC EDGAR | +0.00% | +0.81% | |
| Merrimack Reports Third Quarter 2023 Financial Results | Press release | Business Wire | +0.00% | +0.81% |
Each reaction is the move the market actually made, measured from the news timestamp. Headlines link through to the MACK section they belong to.
Where else MACK is measured.
MACK earnings → · Analyst actions → · SEC filings →
Other Healthcare names, measured the same way
| Ticker | Events | Median 30-min | % positive |
|---|---|---|---|
| Nova Leap Health Corp (NLH_CDNX) | 42 | 0.00% | 20% |
| Regional Health Properties, Inc. (RHE) | 42 | +1.71% | 61% |
| PROTOKINETIX INC (PKTX) | 41 | 0.00% | 14% |
| Vascular Biogenics Ltd. - Ordinary Shares (VBLT) | 41 | -4.03% | 0% |
Same sector, same measurement: percent move vs. the price at the news timestamp, read at 30 minutes. Sample sizes differ, so the medians are comparable but the confidence behind them is not.
All Healthcare names, measured the same way →
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How the numbers are made.
How is Merrimack Pharmaceuticals, Inc.'s median reaction calculated?
Every labeled MACK news event is measured from its own timestamp: the last trade before the news is the base price, and the move is read at fixed horizons — 30 minutes of trading, then the close. The median across 41 events is what this page reports. Point-in-time, zero look-ahead: no event borrows information from a later one.
What counts as a positive reaction?
Any event whose price move is above zero at the horizon, relative to the last trade before the news timestamp. 50% of MACK's measured events are up at 30 minutes; the rest close the window flat or negative.
How often is this page updated?
The news table refreshes automatically as new events are labeled and priced. The reaction medians are re-pulled in batches from the dataset — the figures here are as of 2026-09-21.
Does MACK's past reaction predict its next one?
No. These are realized facts about past events, not forecasts. They describe a distribution — they say nothing certain about any future move.